The United States-Mexican War, 1846-1848

I. Introduction

II. Origins of the U.S.-Mexican War

V. The Treaty of Guadalupe Hidalgo

VI. Legacies, lessons, and perspectives on the war

Recommended resources for the U.S.-Mexican War

About the author

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I. Introduction

President James K. Polk

Throughout the war, as U.S. forces invaded and occupied northern Mexico then captured Mexico City, President James K. Polk maintained that the United States was fighting “a just war.”  In his war message to Congress on May 11, 1846, he charged that Mexican forces had “invaded our territory and shed the blood of our fellow-citizens on our own soil.”  Given the “grievous wrongs perpetrated by Mexico,” said Polk, the United States had no choice but to fight for the “vindication of our rights and defense of our territory.”^[2]  Many prominent Americans at the time disagreed with the president.  Among them were former president John Quincy Adams, future presidents Abraham Lincoln and Ulysses S. Grant, former vice-president John C. Calhoun, and three-time presidential candidate Henry Clay.

Illinois Representative Abraham Lincoln

Two weeks after the president presented his war message, John Quincy Adams delivered a speech in the House of Representatives in which he denounced “this most outrageous war,” charging that its real purpose was territorial aggrandizement and the expansion of slavery.  Illinois congressman Abraham Lincoln, in his first major speech in the House on January 12, 1848, challenged the president’s claim that American blood had been shed on American soil, stating that the evidence fell “far short of proving his justification.”  In his lawyerly fashion, Lincoln presented counter evidence showing that Mexico had a better claim to the disputed territory.  The president himself, Lincoln added whimsically, was a “bewildered, confounded, and miserably perplexed man.”^[3]

Lieutenant Ulysses S. Grant

Lieutenant Ulysses S. Grant was 24 years old when the war broke out.  Leaving his fiancé in Ohio, he served under generals Zachary Taylor and Winfield Scott, participating in major battles in northern and central Mexico.  Grant found no glory in war but rather mourned its waste and loss of life.  Reflecting on his war experiences later in life, he told a journalist, “I do not think there was ever a more wicked war than that waged by the United States on Mexico.”  He reiterated this judgment in his memoirs, describing the war “as one of the most unjust ever waged by a stronger against a weaker nation.  It was an instance of a republic following the bad example of European monarchies, in not considering justice in their desire to acquire additional territory.”^[4]

Whig Party leader Henry Clay

Henry Clay, leader of the Whig Party, was no longer the “war hawk” of 1812.  He had honed his diplomatic skills as secretary of state under President John Quincy Adams and facilitated domestic political compromises as well.  He believed that a compromise with Mexico could have been achieved had Polk negotiated “in a true spirit of amity and conciliation.”  Speaking to a large gathering in Lexington, Kentucky on November 13, 1847, the elder statesman argued that the president had rejected this “pacific and moderate course” in favor of planting U.S. forces “in a warlike attitude” in the disputed territory.  “This is no war of defense,” he declared, “but one unnecessary and of offensive aggression. It is Mexico that is defending her fire-sides, her castles and her altars, not we.”

II.  Origins of the U.S.-Mexican War

The origins of the U.S.-Mexican War fall into two categories.  One derives from a dispute over the border of Texas.  The other, from the Polk administration’s desire to acquire Mexico’s northern territories of Alta California and Nuevo México.  President Polk did not want war per se.  He initially hoped that Mexico would agree to American border claims and sell the desired territories to the United States.  When Mexico refused, Polk provoked a war and took possession of the territories.  According to the diplomatic historian George C. Herring:

Polk and many of his countrymen were determined to have Texas to the Rio Grande and all of California on their own terms. . . . Polk appears not to have set out to provoke Mexico into what could be used as a war of conquest.  Rather, contemptuous of his presumably inferior adversaries, he assumed he could bully them into giving him what he wanted. . . . Certain that an inferior people would be no match for Americans, he envisioned a war of three to four months.  The United States would secure control of Mexico’s northern provinces and use them to force acceptance of the Rio Grande boundary and cession of California and New Mexico.^[7]

Mexico’s troubles

Antonio López de Santa Anna

Mexico achieved independence from Spain on August 24, 1821.  The eleven-year war that led to independence cost the lives of over half a million Mexicans, including one out of every ten fighting-age men.  About half the population of six million were indigenous peoples of various ethnicities, 30 to 40 percent were mestizos (a mixture of Spanish and Native American), and 10 to 20 percent were of Spanish extraction (mostly criollos, born in Mexico).  The country remained impoverished and politically unstable for decades after independence.  According to the Mexican Embassy, “During the next 30 years, Mexico had close to 50 governments, almost all as the result of military coups.  Eleven of them were presided by one man, General Antonio López de Santa Anna.”^[8]  In 1824, Mexico adopted a constitution modeled in part on that of the United States, except Indians were deemed citizens with rights to vote and hold public office.  Mexico effectively banned slavery through a series of laws in the 1820s, which in turn led to an infiltration of runaway slaves from the United States.  By 1840, there were an estimated 6,000 Blacks in the country.  A population census in 1842 indicated a total Mexican population of just over seven million, as compared to about eighteen million in the United States.

Indigenous territories within Mexico, 1830s

The vast stretches of land in the north inherited by Mexico from Spain were home to Comanches, Apaches, Kiowas, Navaho, Hois, Tenewas, Yamparikas, Pueblos, and other tribes.  Mexico’s claim to the region did not negate the right of these indigenous groups to occupy their lands.  Rather, the claim was meant to preclude colonization and exploitation by other European and EuroAmerican powers.  Most of the indigenous peoples in the northern region were hostile to Spanish and Mexican incursions, although not necessarily to trade.  The Mexicans labeled the hostile tribes indios bárbaros (barbarians), in contrast to the peaceful tribes that integrated into the Mexican system, such as the Pueblos.

Mexican states and territories (click to enlarge)

Mexico’s political instability grew worse in the 1830s.  Santa Anna won the presidential election of 1833, but soon switched his allegiance from the liberals to the conservatives and established a caudillo (strongman) state.  The Mexican Congress was dismissed and a new constitution was written in 1836 that centralized power in the federal government.  (The constitution of 1824 had distributed governmental powers among nineteen semiautonomous states and five territories.)  Santa Anna’s authoritarian moves sparked widespread protests and outright rebellion in the states of Coahuila y Tejas, Nuevo León, San Luis Potosí, Sonora, Tamaulipas, Yucatán, Zacatecas, and in the territories of Nuevo México and Alta California.  Tejas separated from Coahuila to form its own Republic of Texas.  General Santa Anna raised an army and defeated a large rebel force in Zacatecas in May 1835, but he was unable to suppress the rebellion in Texas.

The Alamo mission near San Antonio

The Texan fight for independence began in October 1835 and lasted seven months.  The rebel force consisted of Texas Rangers, with much experience fighting Indians, and American volunteers streaming into Texas, included the famous Tennessee congressman David Crocket.  All of the latter acted in violation of the U.S. Neutrality Act of 1818, which forbade private military expeditions, but the Jackson administration ignored the law.  Texan forces were defeated at the old Alamo mission near San Antonio on March 6, 1836, and again at Goliad on March 22, but rallied to defeat Santa Anna’s army at the Battle of San Jacinto on April 21.  The Mexican Army executed 342 prisoners-of-war at Goliad.  Texans responded in kind at San Jacinto, “slaughtering hundreds of unresisting Mexican soldiers,” although the deaths were officially reported as battle deaths (the tally was 650 Mexicans and 11 Texans killed).^[10]

U.S. annexation of Texas

Henry Clay & Theodore Frelinghuysen poster

James K. Polk & George Dallas poster, 1844

President John Tyler (1841-1845) was more amenable to annexation than his predecessor.  Tyler signed a treaty of annexation with Texas in April 1844, but the Senate refused to ratify it, thus leaving the issue hanging as the presidential election approached that fall.  Van Buren was expected to be the Democratic Party nominee, but his opposition to the annexation of Texas led expansionists to push for the relatively unknown James K. Polk.  Polk was a former Tennessee congressman, Speaker of the House (1835-39), and one-term governor, but he had lost the last two gubernatorial elections.  With Andrew Jackson’s support, however, and a few rule manipulations, Polk became the nominee over front runner Van Buren.

Polk ran on an expansionist platform designed to appeal to both southerners and northerners, respectively calling the “re-annexation” of Texas and the “re-occupation” of Oregon territory – misleading terms that implied existing American ownership.  Polk did not mention California or New Mexico while on the campaign trail.  Whig presidential candidate Henry Clay opposed the annexation of Texas without first settling the border dispute with Mexico.  He voiced his opinion in a letter to the National Intelligencer on April 17, 1844:

I certainly am not willing to involve this country in a foreign war for the object of acquiring Texas. I know there are those who regard such a war with indifference, and as a trifling affair, on account of the weakness of Mexico, and her inability to inflict serious injury upon this country.  But I do not look upon it thus lightly. I regard all wars as great calamities, to be avoided, if possible, and honorable peace as the wisest and truest policy of this country. . . . Honor and good faith and justice are equally due from this country towards the weak as towards the strong . . . I consider the annexation of Texas, at this time, without the assent of Mexico, as a measure compromising the national character, involving us certainly in war with Mexico, probably with other foreign powers, dangerous to the integrity of the Union, inexpedient in the present financial condition of the country, and not called for by any general expression of public opinion.^[13]

Clay was expected to win the presidential election in November 1844, but Polk pulled an upset.  Polk won a small plurality of the popular vote, 49.5%, as compared to Clay’s 48.1%, with Liberty Party candidate James G. Birney garnering 2.3%, including 15,800 votes in the state of New York.  According to the historian Brian DeLay, “Had Clay won just 5,107 more votes in New York State from the nearly one million cast, he would have become president and there almost certainly would have been no annexation of Texas, no war with Mexico, no U.S. Civil War, and a vastly different continental story.  But by the narrowest of margins Polk’s vision took the day.”^[14]  Polk’s electoral victory led to a new surge of expansionist fervor in the country.  Sensing the time was right, outgoing President Tyler proposed to Congress that Texas be admitted as a state rather than a territory, thereby requiring majority approval in both houses of Congress rather than two-thirds of the Senate (the last attempt had failed).  The strategy worked and Tyler signed an annexation bill on March 1, 1845, three days before Polk was inaugurated.

General José Joaquín de Herrera

Mexico’s response to the annexation measure was to sever diplomatic relations with the United States.  Mexican president José Joaquin de Herrera issued a proclamation on June 4, 1845, declaring that “annexation of Texas to the United States . . . attacks all the rights that Mexico has to that territory, is an insult to her dignity as a sovereign nation, and threatens her independence and political existence.”  The proclamation decreed, “The Mexican nation calls upon all her children to the defense of her national independence.”  This proclamation has sometimes been interpreted as a declaration of war against the U.S., but it was not.  It was a call to arms in defense of the nation.^[15]  Herrera came to power in late 1844, replacing Santa Anna.  At the time, he issued a manifesto declaring that Santa Anna had failed to prosecute the war against Texas.  The U.S. annexation of Texas, however, dramatically changed the situation. 

President Polk’s expansionist strategy

Sarah and James Polk

The historian Amy S. Greenberg describes James K. Polk as a protégé of Andrew Jackson, a hardworking president, a devoted husband to his wife, Sarah, and a slaveholder who brought his slaves to the White House in 1845.  He was ambitious, meticulous, secretive, and strategic, the latter being essential for realizing his expansionist goals in a complex diplomatic and political environment.  Polk undertook two very different approaches toward Great Britain and Mexico.  Toward Great Britain, he feigned war while pursuing a negotiated settlement on the division of the Oregon territory.  Toward Mexico, he expressed peaceful intentions while actively preparing for war, his goals being not only to obtain the expansive border claims of Texas but also the Mexican territories of California and New Mexico.  Although Polk said nothing about California on the campaign trail, he confided to his cabinet in the first days of his presidency that the acquisition of California was one of his main objectives.  The territory had fertile lands, rich deposits of minerals, and fine harbors that would facilitate the expansion of trade across the Pacific Ocean.

With regard to the Oregon territory, Polk encouraged the saber-rattling rhetoric of “Fifty-four forty or fight!” (referring to the upper latitude of the jointly held Oregon territory) in order to pressure Great Britain to back down on its proposed dividing line of the Columbia River.  Polk wanted the boundary further to the north and suggested to the British the 49^th parallel, which was far below 54-40 latitude.  According to the American diplomatic historian William Weeks:

He fomented Democrats from the Northwest such as Edward Hannegan of Indiana and William Allen of Ohio to demand all of Oregon, assuring them that he would never back down from the claim to 54-40 even though he planned all along to use their extreme claims to form the basis of a compromise at 49 degrees. . . . Here the president benefited from the demonstrated willingness of Americans to fight even when a lack of preparedness and plain common sense seemed to preclude that option, and indeed, the chest-thumping assertions of Hannegan, Allen, and others bore some resemblance to the War Hawks of 1812.  Polk, unlike Madison, was not controlled by hotheads in Congress but rather used their threats to help extract a deal.^[17]

Polk’s strategy toward Mexico was just the opposite of his strategy toward Great Britain and Oregon.  Instead of talking loudly and negotiating quietly, Polk talked softly and struck with force.  Prior to the onset of war, Polk promised the American people that any expansion of the nation’s boundaries into Mexican territory would be undertaken “not as the conquest of a nation seeking to extend her dominions by arms and violence but as the peaceful acquisition of a territory once her own.”  At the same time, he began preparing for war, sending U.S. forces into the disputed territory and reinforcing naval squadrons in the Gulf of Mexico and Pacific Ocean.  How much force would be needed to convince the Mexican government to give up its northern territories could not be foretold.  In November 1845, he sent emissary John Slidell to Mexico City, ostensibly to negotiate with the Mexican government but actuality to demand that Mexico accept the exaggerated border claims and sell Alta California and Nuevo México.  As Weeks notes:

If Polk bluffed war and sought peace with Great Britain, it was very much the reverse as concerns the Republic of Mexico. . . . First, he had to appear to try to resolve the differences with Mexico via negotiation.  To that end, he dispatched John Slidell of Louisiana to Mexico City to negotiate the range of issues separating the states.  In truth, Slidell went not to negotiate but to dictate.  He demanded that Mexico drop its protests against the annexation of Texas, recognize its boundary at the Rio Grande del Norte, and agree to sell California ($25 million) and New Mexico ($3 million) to the United States.  In exchange for these extravagant demands, the Polk administration stood ready to assume the nearly $2 million in Claims that American citizens held against the Mexican government for private property seized during the course of the numerous revolutions since 1821.^[18]

General Taylor’s camp at Corpus Christi

Polk began military maneuvers in July 1845.  Without authorization from Congress, he directed General Zachary Taylor and 4,000 troops to advance to the south bank of the Nueces River, near Corpus Christi.  Six months later, on January 13, 1846, before learning of the outcome of John Slidell’s mission in Mexico City, Polk ordered Taylor to proceed further to the Rio Grande, thus entering disputed territory.  As Polk later wrote in his diary, he anticipated “a collision between the American and Mexican forces.”^[19]  Taylor’s troops set up camp on the north side of the Rio Grande, opposite the town of Matamoros, on March 28.  They built a makeshift fort, aimed their artillery at the town, and blockaded the mouth of the river, denying food and supplies to 4,000 townspeople and 3,400 Mexican soldiers stationed there.  Apart from entering into what Mexicans considered their territory, the blockade itself was an act of war.  According to the historian Glenn Price:

The first indisputable act of war was an act of the United States, when its naval forces blockaded the Rio Grande on 12 April 1846.  Even had the land on the left bank of that river been within the limits of the United States, to blockade the river, which in that case would have been the international boundary, was an act of war.  That conclusion needs no supporting argument, but it may be of interest to point out that the United States government was on record as stating that any attempt by Mexico to close the river to American traffic would justify hostilities.  Instructions given General Zachary Taylor by the Department of War stated that “the Rio Grande, in a state of peace, may be regarded as equally open to navigation of the U.S. & Mexico,” and should this “reciprocal right be resisted by Mexico,” Taylor was at liberty to force it open by military power.^[20]

Onset of war

Mariano Paredes y Arrillaga

General Mariano Paredes y Arrillaga replaced Herrara as president of Mexico in December 1845.  He immediately found himself in the same dilemma as his predecessor, having no means of stopping the United States from moving into (disputed) Mexican territory while nonetheless being pressured by the public to uphold national honor and exert a valiant defense of the homeland.  Paredes dismissed Slidell in March 1846, explaining to him that the presence of American troops on Mexican soil made negotiations impossible.  Slidell also lacked proper credentials and had come with an additional agenda other than negotiating the border dispute.  Paredes demanded that U.S. forces return to the north side of the Nueces River, but he nevertheless sought to reassure the U.S. of his intentions by issuing a manifesto declaring that he “would never commit a single aggression against the United States,” but only act in defense of Mexico.^[21]

Battle of Palo Alto, May 8, 1846

On April 23, with the American troops encamped opposite Matamoras and having blockaded the river, Paredes issued another manifesto, this time declaring that “from this day defensive war begins.”  The following day, the Mexican commander at Matamoros, General Arista, informed Taylor that hostilities had commenced.  On April 25, Mexican troops crossed the river and attacked a U.S. patrol unit, killing eleven men.  Full-blown battles followed at Palo Alto and Resaca de la Palma on May 8 and 9, both of which U.S. forces won.

US House of Representatives

On Monday, May 11, President Polk presented his war message to Congress.  He blamed Mexico for the outbreak of hostilities and declared that he had done everything in his power to avoid war.  He did not ask Congress for a formal declaration of war, as required in the Constitution, but stated that war already existed and asked Congress for money to supply troops in the field.  Representative Linn Boyd, Democrat of Kentucky, introduced an amendment to the war bill paraphrasing the president, declaring that “a state of war existed” between Mexico and the United States.”^[24]

Rep. Joshua Giddings

Representative Joshua Giddings of Ohio, an abolitionist and ally of John Quincy Adams, refused to be intimidated into voting for Polk’s war bill on the skewed basis of providing for troops in the field.  He charged that Polk’s aggressive maneuvers were designed to provoke a war with Mexico and that Polk’s ultimate goal was the conquest of Mexico and California.

In the murder of Mexicans upon their own soil, or in robbing them of their country, I can take no part, either now or hereafter.  The guilt of these crimes must rest on others; I will not participate in them; but if Mexicans or any other people should dare invade our country, I would meet them with the sword in one hand and a torch in the other . . . We may always justify ourselves for defending our country, but never for waging a war upon an unoffending people for the purpose of conquest.  There is an immutable, an eternal principle of justice pervading the moral universe.  No nation, or people, or individual ever did or ever will violate that law with impunity.^[26]

Senator Thomas Clayton

The Senate debated the war bill for two days.  Senator Thomas Clayton of Delaware, a Whig, laid out the main arguments of opponents; namely, that the president had initiated hostilities without consulting Congress and that moving U.S. forces into disputed territory was an act of aggression on the part of the U.S.:

I do not see on what principle it can be shown that the President, without consulting Congress and obtaining its sanction for the procedure, had a right to send an army to take up a position, where, as it must have been foreseen, the inevitable consequences would be war. . . . The question is, Was it proper?  Was it right?  . . . Why was it necessary to cross the desert, and take up a position immediately in front of the friendly town of Matamoros?  Why was it necessary to take up that position, with the batteries pointed against the town at a distance of not more than five hundred yards from its environs?  It was an aggressive act; an act which the civilized world will designate.  It was as much an act of aggression on our part as is a man’s pointing a pistol at another’s breast. . . . I have felt that these acts of the Executive ought to be condemned – I do condemn them.  I think that they will be condemned by the people of the United States.  By these acts we have been precipitated into a war with a friendly nation.^[27]

In the end, the Senate voted 40-2 to approve supplies for the troops (coupled with the acknowledgement that war existed), and the House voted 174-14, with 35 abstentions.  These tallies, however, hardly reflected the strength of the opposition.  As the historian John H. Schroeder explains:

As sensitive politicians, most administration critics could not vote their consciences at the expense of their patriotism.  Because they understood that national public opinion would be outraged and demand retribution for the attack on the Rio Grande, the opposition dared not risk charges of failing to support an endangered American army.  That fear of being labeled disloyal was the foremost consideration in the minds of dissidents.^[28]

In presenting his war bill to Congress, Polk made no mention of his desire to obtain California and New Mexico.  According to the historian Ballard C. Campbell, Polk’s “interest in using the war for territorial gain was not publicly disclosed until August 1846, when the president asked Congress to approve a $2 million appropriation that could be used as partial payment to Mexico for territory – or perhaps a bribe to Santa Anna.”^[29]

Underlying causes:  race, history, and “Manifest Destiny”

Recruitment poster, Boston

The U.S. Army had less than 7,400 soldiers in early 1846.  The war bill passed by Congress on May 13, 1846, authorized the president to enlist 50,000 “volunteers” for twelve months.  Many young men jumped at the opportunity, egged on by the pro-war press.  Walt Whitman, the 27-year old editor of the Brooklyn Daily Eagle and later a famed poet, called for revenge against Mexico in an editorial on May 11, 1846:

Yes: Mexico must be thoroughly chastised!  We have reached a point in our intercourse with that country, when prompt and effectual demonstrations of force are enjoined upon us by every dictate of right and policy. . . . Let our arms now be carried with a spirit which shall teach the world that, while we are not forward for a quarrel, America knows how to crush, as well as how to expand!^[31]

The desire to “crush” Mexico had racial, historical, and ideological overtones.

Most Anglo Americans viewed Mexicans as an inferior race based on their mixed, Spanish-Indian ancestry.  While not scorned as “savages,” they were depreciated as “an idle, thriftless people” who did not deserve to rule over the lands they held in North America.^[32]  Some viewed the inability of Mexicans to pacify hostile tribes as confirmation of their inferiority.  Perpetual disorder in the Mexican government furthermore prompted predictions that Americans would one day rule Mexico.  William Seton “Guy” Henry, an American journalist who covered the war, wrote of the Mexican people:

The finger of Fate points, if not to their eventual extinction, to the time they will cease to be the owners of the soil, and when the Anglo race will rule with republican simplicity and justice, a land literally “flowing with milk and honey” – who will, by their superior mental and physical abilities . . . populate the country with a race of men who will prove the infinite goodness of our Maker, in creating nothing but what is for use and some good purpose.”^[33]

Recruitment poster, Holmes County, Ohio

Anglo American racism created substantial barriers to peacefully resolving outstanding issues with Mexico through negotiations.  Not only was there a widespread belief among Americans that the “inferior” Mexican people must sooner or later give up their lands to the superior “Anglo race,” but the very idea of sitting down at a table and talking as equals was anathema to many.  According to Glenn Price, “The attitude was that there was very little difference between an Indian and a Mexican; serious and respectful diplomacy was out of place in either case.”^[34]  For Polk and many other Americans in that intensely racist era, the mere fact that brown-skinned Mexicans expected to be treated as equals constituted a challenge to the assumed racial hierarchy of Anglo (white) dominance.  Polk and company expected Mexicans to accept their status as an “inferior race” and give in to the demands of the “superior race.”  Indeed, Mexico’s failure to do so was deemed a sufficient cause for war.  According to the historian Amy Greenberg, “Polk viewed international relations through the lens of slaveholding and dominance”:

Polk’s concept of justice was unquestionably shaped by his experience as a slavemaster.  Some slaveholders, such as Henry Clay, or Thomas Jefferson a generation before, struggled with the knowledge that slavery was wrong.  But like most intensely conservative slave masters in the 1840s, Sarah and James Polk believed the domination of white over black was part of God’s plan. . . . Domination of the strong over the weak, and white over black or brown, was not just the reality of slavery, it was also, in their perspective, right.^[35]

“Let the half-civilized Mexicans hear the crack of the unerring New Hampshire riflemen.”

Outspoken Anglo American racism coupled with American aggression evoked fear in Mexico.  The editors of a Chihuahua newspaper expressed the view in 1841 that if Mexico failed to stop the United States from annexing Texas, Anglo Americans would not only gobble up more Mexican territory but also establish a different religion on Mexican soil and sell Mexican citizens “as beasts” because “their color was not as white as that of their conquerors.”  The editors of El Siglo Diez y Nueve wrote in May 1844 that the United States was populated by a “race that had no mercy for others.”  They pointed out the hypocrisy of Americans proclaiming liberty for all while annihilating Indians and enslaving Blacks.  The Americans, warned El Siglo, would not be content with merely acquiring Mexican soil; they would only be satisfied when the “Mexican race” was destroyed.^[37]  Such views explain why many Mexicans demanded that their government fight the U.S. despite Mexico’s military weakness, rather than give in to American aggression.

The American desire to “crush” Mexico was also rooted in the historical memory of Mexican atrocities committed at the Alamo and Goliad.  Similar atrocities committed by U.S. soldiers at San Jacinto were forgotten or viewed as just revenge.  According to the American military historian John Eisenhower:

During the nine years between the Battle of San Jacinto and the U.S. offer of annexation to Texas, the government of the United States always maintained a proper neutrality between Texas and Mexico.  The American people, however, observed no such inhibitions.  They openly sympathized with the Anglo-Saxon émigrés whom they now considered Texans; they supplied Sam Houston’s army with weapons; and though brutality occurred on both sides, the Americans sided with the Texan version on every controversial issue.  As a result the American public grew progressively more antagonistic toward Mexico as a nation.  Mexicans came to be considered less than “civilized” people, undeserving of rights generally accorded to Europeans.  It is not surprising, therefore, that rationalizing unjust acts against Mexico would become easy.^[38]

John O”Sullivan

A third factor influencing American attitudes toward Mexico was the ideology of “manifest destiny,” which combined religious, political, and racial ideas into a righteous justification for American territorial expansion.  The most famous proponent of this informal ideology, John O’Sullivan, editor of the United States Magazine and Democratic Review, expressed the view that U.S. expansion was divinely ordained; that it would extend freedom, democracy, and civilization to new lands; and that more land was needed for a rapidly growing Anglo-Saxon population.  In asserting this presumed mandate from heaven, O’Sullivan made the case that America represented a new order of civilization, as compared to Old World empires, and that the American character was inherently noble and good.  As he wrote in 1839:

What friend of human liberty, civilization, and refinement can cast his view over the past history the monarchies and aristocracies of antiquity, and not deplore that they ever existed?  What philanthropist can contemplate the oppressions, the cruelties, the injustice inflicted by them on the masses of mankind, and not turn with moral horror from the retrospect? America is destined for better deeds.  It is our unparalleled glory that we have no reminiscences of battle fields but in defense of humanity, of the oppressed of all nations, of the rights of conscience, the rights of personal enfranchisement.  Our annals describe no scenes of horrid carnage where men were led on by hundreds of thousands to slay one another, dupes and victims to emperors, kings, nobles, demons in the human form called heroes.  We have had patriots to defend our homes, our liberties, but no aspirants to crowns or thrones, nor have the American people ever suffered themselves to be led on by wicked ambition to depopulate the land, to spread desolation far and wide, that a human being might be placed on a seat of supremacy.^[39]

This flattering view of American history and identity ignored much actual history, including the recent forced removal of Native American tribes that caused thousands of deaths.  Nor was it true that democratic governments eschewed aggression and imperialism.  George C. Herring comments:

Dubious when it was written, O’Sullivan’s affirmation soon proved completely wrong.  The Mexican-American conflict of 1846-48 was in large part a war of lust and aggrandizement.  The United States had long coveted Texas.  In the 1840s, California and New Mexico also became objects of desire.  With characteristic single-mindedness, Polk set his sights on all of them.^[40]

The United States, in other words, was becoming more like Old World empires, except that a president rather than a king was leading the nation into “scenes of horrid carnage.”  O’Sullivan coined the particular catchphrase “manifest destiny” in the July-August 1845 issue of the United States Magazine and Democratic Review, just after Texas was annexed to the U.S.  The slogan was quickly picked up by other expansionists who used it to embellish American territorial ambitions with noble ideals.  One such expansionist was the president of the United States, James Polk.  In his Third Annual Message to Congress on December 7, 1847, he said:  “No country has been so much favored, or should acknowledge with deeper reverence the manifestations of the divine protection.  An all-wise Creator directed and guarded us in our infant struggle for freedom and has constantly watched over our surprising progress until we have become one of the great nations of the earth.”^[41]

Elder statesman Albert Gallatin

Among those who called attention to the banality of “Manifest Destiny” was Albert Gallatin, former congressman, secretary of the treasury, and foreign minister, who wrote at the age of eighty-seven, “What shall be said of the notion of an empire extending from the Atlantic to the Pacific, and from the North Pole to the Equator?  Of the destiny of the Anglo-Saxon race, or its universal monarchy over the whole of North America?”  Such “allegations of superiority of race and destiny neither require nor deserve any answer; they are but pretenses under which to disguise ambition, cupidity, or silly vanity.”^[42]  Abolitionists also held forth a different vision the nation’s progress, one that extended freedom and democracy to three million people enslaved in the United States.  Peace advocates, too, conceived of progress in different terms.  They envisioned a time when war would be transcended through “the general use of conciliation, arbitration, judicial methods, and other peaceful means of avoiding and adjusting differences among nations,” as stated in the 1828 charter of the American Peace Society.^[43]

III.  Costs and conduct of the war

War news from Mexico (1851 hand-colored engraving by Richard Caton}

The U.S.-Mexican War was documented like no other war in history up to that time.  At least eighteen American journalists were embedded in U.S. Army units during the war.  Hundreds of soldiers wrote letters and dozens were christened “occasional” or “special” correspondents for mass circulation newspapers.  Americans also established newspapers in occupied Mexican cities.  The public’s demand for eyewitness accounts of battles and first hand news of the war was insatiable.  Even antiwar editor Horace Greeley of the New York Tribune felt obliged to print every detail of battle, as “carnage” is what sold newspapers.  Newspapers also published lists of casualties, often gathered by journalists, which were more fearfully awaited.  News from Mexico took at least ten days to reach New Orleans, after which it was distributed by steamship, rail, or horseback to other cities (telegraph lines were in their infancy).  It took another eight days to reach Washington from New Orleans.^[45]

Literate U.S. Army regulars

About 90,000 U.S. soldiers served in Mexico during the war; no more than 43,000 at any one time.  Approximately 31,000 were Army regulars while 59,000 were part of “volunteer” state regiments.  About 40% of the regulars were immigrants, mainly Irish.  According to records of the U.S. General Recruiting Service for 1840-49, 35% of the regulars could not sign their own names.  All black men were excluded from the U.S. Army, while the U.S. Navy imposed a quota of five percent.  Black servants were nonetheless part of many army units.  Lieutenant Ulysses S. Grant wrote from New Orleans to his fiancé, Julia Dent, “I have a black boy to take along as my servant that has been in Mexico.  He speaks English, Spanish and French.  I think he may be very useful where we are going.”  Some southern officers brought their slaves with them and some northern officers employed slaves as their servants.  Although not formally enrolled as soldiers, some servants took part in battles and were wounded.  A few escaped in Mexico.^[47]

Casualty list in the Charleston Courier (click to enlarge)

The casualty rate for soldiers was extremely high on both sides.  Of the 90,000 U.S. soldiers who served in Mexico, nearly 14,000 died, a death rate of 15.5%, or one out of every seven soldiers.  According to Eisenhower, this was “the highest death rate of any war in our history.”^[50]  On the Mexican side, the death rate was even higher, although figures are less precise.  Of some 82,000 men who served in the Mexican army or were guerrillas, an estimated 25,000 lost their lives, an astounding death rate of 31%, or almost one out of every three soldiers.  These figures do not include Mexican civilian deaths, the number of which is unknown.  As Mexican armies included many women and wives who assisted the soldiers, they were subjected to the travails of exposure, hunger, and disease as well.^[51]

American casualties

• Total number of U.S. soldiers who served in Mexico:  89,836 (Regulars: 31,024; Volunteers: 58,812)
• Deaths during the war:  13,962 (15.54%)
• Killed in action or died of wounds: 1,733
• Died of disease or other causes:  12,229
• Wounded:  4,152

Mexican casualties

• Total number of Mexican soldiers mobilized:  82,000
• Total number who died during war:  25,000 (30.5%)
• Killed in action or died of wounds:  5,000
• Died of disease or other causes:  20,000
• Missing:  10,000

Disease was the biggest killer in the war.  For every U.S. soldier who died in battle or from battle wounds, seven died of disease.  “As was typical for other 19^th-century conflicts,” writes the American military historian Derek R. Mallett, “infectious disease accounted for far more deaths than battle trauma.  Yellow fever, malaria, dysentery, and epidemic measles, mumps, and even occasional smallpox were problems both on campaign and in camp.”^[52]  Much illness resulted from drinking tainted water from polluted streams, a situation exacerbated by a shortage of wood to make fires and boil water.  Soldiers also needed better tents and medical care.  This became apparent during the nine months that General Taylor’s troops spent camping near Corpus Christi (July 1845 to March 1846).  According to Foos:

Dysentery and fevers raged through the camp until one-sixth of the men were on sick report, and about one-half suffered from some degree of infirmity.  The tents provided by the Quartermaster’s Corps were worn and rotten . . . The border region suffered from frequent “northers,” fierce storms that could drop the temperature from ninety degrees to below freezing in a matter of hours.  The men slept in mud and cold water, the quartermasters having neglected to provide floors for the tents.^[53]

To these indignities were added late pay from the Quartermaster and swarms of “camp followers” – liquor sellers, gamblers, prostitutes, and criminals – intent on quickly relieving soldiers of their pay, and sometimes robbing and assaulting them.  Taylor could do little to disperse this rabble in Corpus Christi as civilians were subject only to civil authority.  Desertions were common on both sides.  The number of U.S. deserters is estimated at 9,200, about ten percent of the regulars and nearly seven percent of the volunteers.^[54]  This is the highest desertion rate in any American war.

Commemorative plaque in Mexico City honoring 71 members of the San Patricio Battalion

The most famous, or infamous, of the American deserters was John Riley, a recent Irish immigrant and former non-commissioned officer in the British Army.  Troubled by a war against fellow Catholics, and offered incentives to defect by Mexican authorities, Riley and forty-eight soldiers, mostly Irish-American, deserted General Taylor’s camp across from Matamoros before the first shot was fired.  Joined by other Irish and German deserters and a few escaped slaves, Santa Anna organized the soldiers into an artillery battalion in November 1846.  The San Patricio Battalion fought tenaciously in battles at Monterrey, Buena Vista, Cerro Gordo, and Churubusco.  The U.S. Army captured and executed fifty members of the battalion, but Riley’s life was spared, as he had deserted before the war officially began.  His punishment consisted of being whipped and branded with a “D” on his face.  The San Patricio Battalion has been honored in Mexico in commemorations and on St. Patrick’s Day.  In 2002, Mexico’s Chamber of Deputies inscribed in gold letters on its Wall of Honor, “Defensores de la Patria 1846-1848 y Batallón de San Patricio” (Defenders of the Motherland 1846-1848 and the San Patricio Battalion).

Mexican lancers and infantry

Mexican troops often outnumbered U.S. troops on the battlefield but failed to win a single major battle in terms of forcing an American retreat.  The Mexican army had antiquated short range artillery and often ran short of ammunition.  American long-range artillery eviscerated Mexican units at a distance and thwarted Mexican charges.  The U.S. Army also had more highly trained officers and engineers, and was far better supplied than Mexican forces, notwithstanding many limitations.  Mexican troops were literally starving at times.

Military campaigns and occupations

• directing General Zachary Taylor to take control of the northeastern region of Mexico, beginning with the town of Matamoros;
• sending Colonel Stephen W. Kearny and some 1,600 soldiers from Fort Leavenworth, Kansas, to secure the northern territories of Nuevo México and Alta California, and dispatching naval forces in the Pacific to assist in the capture of California; and
• ordering a naval blockade of Mexico’s Gulf ports so as to deprive the central government of its major source of revenue, import duties.

Popular U.S. culture thrived on stories of American heroism and Mexican treachery, eliding the fact that U.S. troops were invading and occupying Mexico

The American occupation of Mexico was accompanied by much abuse and violence against Mexican civilians.  This violence falls into four categories:

• Personal violence – the abuse of civilians by individual soldiers, including robbery, rape, and murder.  This unscripted, wanton violence was especially prevalent in Taylor’s northeastern campaign, despite efforts by U.S. officers to stop it.

• Counter-insurgency violence – the extension of anti-guerrilla operations to civilians, including revenge attacks, torture, and intimidation; aimed at negating civilian support for guerrillas and extracting information as to their whereabouts.  As guerrilla warfare was deemed outside the rules of civilized combat, special U.S. counterinsurgency units engaged in “uncivilized” methods with tacit approval by commanders.

• Collateral war violence – war operations such as bombardments and sieges of cities that result in extensive civilian casualties and property damage.  The U.S. bombardment of Veracruz under General Scott stands out as one of the more egregious examples of “collateral damage,” as hundreds of civilians were killed or wounded.

• Structural violence – official policies that impoverish, oppress, or humiliate the civilian population, including taxing the population to support the U.S. occupation and imposing martial law.  Both Taylor and Scott imposed martial law on Mexican towns but, to their credit, refused to take provisions from the civilian population without paying for them.

General Taylor and the occupation of northeastern Mexico

Major-General Zachary Taylor

General Zachary Taylor’s occupation of northeastern Mexico began on May 18, 1846, when his troops crossed the Rio Grande and took control of Matamoros unopposed.  The Mexican army led by General Arista had retreated to the interior the night before, being short of every kind of provision.  In June, Taylor began receiving reinforcements, mainly volunteer regiments, in anticipation of moving on to other towns.  He waited until August for the arrival of steamboats to move his troops and supplies to Camargo, 80 miles upriver.  The waiting period proved hazardous for the 4,000 residents of Matamoros.  According to the U.S. Army military historian General John S. Brown:

As the boredom of garrison duty began to set in, plundering, personal assaults, rape, and other crimes against Mexicans quickly multiplied.  During the first month after the volunteers arrived, some twenty murders occurred.  Initially, Taylor seemed uninterested in devising diversions to occupy his men and failed to stop the attacks.  As thefts, assaults, rapes, murders, and other crimes perpetrated by the volunteers mounted and Taylor failed to discipline his men, ordinary Mexican citizens began to have serious reservations about the American invasion.  Taylor’s lackadaisical approach to discipline produced an effect utterly unanticipated by the Polk administration, many of whose members, particularly pro-expansionists such as Secretary of the Treasury Robert J. Walker, believed that Mexicans would welcome the Americans as liberators. Instead, public opinion turned against the Americans.^[58]

Town of Matamoros

General Taylor’s inclination was to treat the Mexican population with humanity.  He ordered that provisions be purchased at full market value, thereby currying favor with the local business community.  Taylor also established a newspaper, written in Spanish and English, called Republic of the Rio Grande and Friend of the People.  Yet Taylor’s control over his volunteer units left much to be desired.  Lieutenant Ulysses S. Grant, in a letter to his letter to his fiancé, noted that a ”great many murders” had been committed against Mexican civilians in Matamoros in recent weeks, and that U.S. officers in charge had failed “to prevent frequent repetitions.”

Some of the volunteers and above all the Texans seem to think it perfectly right to impose upon the people of a conquered City to any extent, and even to murder them where the act can be covered by the dark.  And how much they seem to enjoy acts of violence too!  I would not pretend to guess the number of murders that have been committed upon the persons of poor Mexicans and the soldiers, since we have been here, but the number would startle you.^[59]

News reporters caught wind of the mayhem.  In mid-July 1846, the journalist George Kendall of the New Orleans Picayune reported from Matamoros, “Several Mexicans were killed in rows last night – some say five or six – by drunken brawlers who hang about the camp of the Texans.”  Kendall’s colleague, Christopher Haile, commented on the rising attacks against the American volunteers, observing that the inhabitants “appear sullen and inclined to seek revenge . . . they hate us cordially.”  Guy Henry, a writer for the New York magazine, Spirit of the Times, offered a more sympathetic view of Mexicans after visiting hospitals in Matamoros.  “I left the hospital shocked with the horrors of war,” he wrote.  The hospitals were “filled with wounded and dying” Mexican soldiers, their amputated limbs confirming the effectiveness of American artillery at the battles of Palo Alto and Resaca de la Palma.^[60]

Mexican surrender at Monterrey

Having set up a supply depot at Camargo, Taylor’s next objective was to capture the fortified city of Monterrey, defended by 7,300 troops under General Pedro de Ampudia.  Taylor arrived with about 6,600 soldiers, having left behind 4,000 volunteers in Camargo.  The 10,000 residents of Monterrey had just celebrated the 250^th anniversary of the city’s founding on September 20, 1596.  Taylor’s forces struck on September 21.  After three days of bombardment and fighting, with each side suffering some 450 casualties, Ampudia offered to surrender the city on condition that his troops be allowed to withdraw without harm and that an eight-week armistice go into effect.  Taylor accepted the terms, half-expecting that a political settlement would ensue.

Despite Taylor’s inclination to treat the population well, the American occupation of Monterrey quickly deteriorated.  Within two weeks, the governor of Nuevo León complained to General William J. Worth that American volunteers were abusing the inhabitants, even killing civilians “without mercy or reasonable motive.”  Such abuse troubled U.S. officers, who anticipated retribution.  Lieutenant George Meade, in a letter to his wife on October 20, 1846, wrote that American volunteers “have made themselves so terrible by their previous outrages as to have inspired the Mexicans with a perfect horror of them.”^[65]  The retribution was not long in coming, as John Brown notes:

The local populace increasingly appeared more than willing to support and shield the guerrillas.  The volunteers’ racism, anti-Catholicism and violence provided all the motive that locals needed to oppose the American advance.  Guerrilla attacks grew more frequent after the battle for Monterrey, when Brig. Gen. William J. Worth . . . discontinued military patrols in the town for a short time, allowing a bloodletting to occur.  Observers estimated that volunteer troops killed some 100 civilians, including many who had been killed by Col. John C. Hays’ 1st Texas Mounted Volunteers.

Texas Ranger (wood engraving 1848)

The Texas Rangers were the most notorious of the volunteer units.  According to Brown, “The Rangers hoped either to find and eliminate the guerrillas or to terrorize the local people to such an extent that they would stop supporting the irregulars.”^[66]  Commanding officers did little to control the Rangers, as their skills as scouts and guerrilla fighters were highly valued.  Indeed, Texas Ranger units were parceled out to every army division.

The fall of Lt. Col. Henry Clay, Jr. at the Battle of Buena Vista

With Monterrey secured, Taylor extended the American occupation to other northeastern towns and cities.  General John E. Wool, who recently arrived from San Antonio, was ordered to take charge of Parras; General Worth was directed to Saltillo; and Taylor proceeded to Victoria, 175 miles south of Monterrey.  Taylor soon had to backtrack, however, as Santa Anna had intercepted a letter revealing that half of Taylor’s army was departing to join General Scott’s impending invasion on the east coast.  Recognizing Taylor’s vulnerability, Santa Anna hastily organized a force of nearly 20,000 soldiers at San Luis Potosí.  On the punishing 250-mile hike north to Buena Vista, nearly one-fourth of his army deserted or died.  The survivors arrived hungry and exhausted. 

News of Buena Vista

One week after the Battle of Buena Vista, the last formal battle in the northeast region took place outside the city of Chihuahua.  Col. Alexander W. Doniphan and some 1,000 soldiers, having made their way from Santa Fe, defeated a Mexican force of comparable size and took charge of the city.  Doniphan arranged for American merchants to be established and kept watch for guerrilla activity during his two month stay.  With many of his volunteer enlistments ending soon, he took his regiment to Saltillo on April 28, allowing the Mexican governor of the state to take charge of the city.

General John E. Wool

General Wool, as military governor of Saltillo, added to the oppression by instituting a policy that held whole towns responsible for any stolen U.S. Army goods, threatening the residents with large fines.  The innocent, as such, were made to pay for the guilty.  “Within a few months,” notes Brown, “Wool collected more than $8,000 in fines, as well as livestock and other personal property.^[69]  General Wool also made an effort to crack down on reckless American violence and abuse.  He imposed stricter discipline, instituted curfews, tried to keep troops away from population centers, and threatened disobedient soldiers with discharge.  Judging by news reports, however, these measures were not enough.  John Durivage, a correspondent for the New Orleans Picayune stationed in Monterrey, wrote on April 25, 1847:

You have published accounts of the disgraceful outrage perpetrated before the battle of Buena Vista, and will be no less shocked to learn that an equally sickening scene of outrageous barbarity has been perpetrated in this region by persons calling themselves Americans.  It appears that near a little town called Guadalupe, an American was shot two or three weeks ago; and his companions and friends determined to revenge his death.  Accordingly a party of a dozen or twenty men visited the place and deliberately murdered twenty-four Mexicans.^[70]

General Taylor confirmed the lawless personal violence in a dispatch to the War Department on June 16, 1847:

I deeply regret to report that many of the twelve months’ volunteers, in their route hence to the lower Rio Grande, have committed extensive depredation and outrages upon the peaceable inhabitants.  There is scarcely a form of crime that has not been reported to me as committed by them . . . Were it possible to rouse the Mexican people to resistance, no more effectual plan could be devised than the very one pursued by some of our volunteer regiments.^[71]

Early photo of U.S. soldiers entering Saltillo

President Polk’s blunt strategy for dealing with the difficulties of occupation was to win the war as quickly as possible and get out.  In public pronouncements he gave no indication of the problems of occupation.  In his Second Annual Message to Congress in December 1846, he praised “our volunteer citizen soldiers, who so promptly responded to their country’s call, with an experience of the discipline of a camp of only a few weeks, have borne their part in the hard-fought battle of Monterrey with a constancy and courage equal to that of veteran troops and worthy of the highest admiration.”  There was no mention of discipline problems or abuses, or efforts to correct these.  His message the following year was much the same.  “Too much praise can not be bestowed upon our officers and men, regulars and volunteers, for their gallantry, discipline, indomitable courage, and perseverance, all seeking the post of danger and vying with each other in deeds of noble daring.”^[72]

The “Army of the West” in Nuevo México and Alta California

Col. Stephen Kearny

Col. Stephen Kearny’s “Army of the West” thus entered Santa Fe unopposed on August 18, 1846.  In a display of power, Kearny’s troops marched in, sabers drawn, with cannons firing in the distance, and hoisted the American flag over the governor’s palace.  Joseph Magoffin, an aide to Col. Kearny who later became mayor of El Paso, indicated in his official report that the Americans were graciously received by the inhabitants:  “Gen’l. Kearny entered this city on 18^th 5 o’c P.M., the authorities & people of the place being ready to give him a hearty welcome.”^[75]  Lieutenant Richard Smith Elliott, a correspondent for the St. Louis Reveille, looked more closely at the reactions of the residents:

Our march into the city . . . was extremely warlike . . . From around corners, men, with surly countenances and downcast looks regarded us with watchfulness, if not terror. . . . Strange, indeed, must have been the feelings of the citizens, when an invading army was thus entering their home . . . all the future of their destiny vague and uncertain – their new rulers strangers to their manners, language and habits, and, as they had been taught to believe, enemies to the only religion they had ever known. . . . As the American flag was raised, and the cannon boomed its glorious national salute from the hill . . . a sigh of commiseration, even for causeless distress, escaped from many a manly breast, as the wail of grief arose above the din of our horses’ tread, and reached our ears from the depth of the gloomy-looking buildings on every hand.^[76]

However exaggerated Magoffin’s account, the Indian threat did, in fact, create a measure of cooperation between the occupying American forces and New Mexicans.  On September 18, Kearny initiated a campaign against the Navajos, his forces augmented by sixty-five Mexican and Pueblo Indian volunteers.  The campaign quickly shifted to negotiations, resulting in a treaty of “permanent peace, mutual trust and friendship” on November 22.  Col. Alexander Doniphan signed the treaty on behalf of the United States.  Fourteen Navajo chiefs signed with an “X,” persuaded no doubt by the American purchase of several hundred sheep and cattle from the Navajos. Col. Kearny had meanwhile departed for California on September 25, leaving Col. Sterling Price in charge of a reduced regiment.  Before leaving, Kearny sent a report to President Polk assuring him that civil government had been established and order secured in New Mexico.  The assurance was premature. Although Kearny’s occupation was considerably less abusive than that of Taylor in the northeast region, the occupation was nevertheless unwanted and eventually resisted.  According to one account:

Bored U.S. troops, overcrowded in Santa Fe, started to attack New Mexican civilians; racial tensions escalated (in their memoirs of the conquest a number of U.S. soldiers made ugly statements expressing contempt for Mexicans).  Some New Mexicans regretted not having offered more resistance when the U.S. army took possession of the territory.  Now they planned revolts.  In December, officials uncovered a plot to overthrow the occupation forces and assassinate Governor [Charles] Bent.  The conspirators were quickly arrested, and the guard was doubled at the governor’s palace.^[79]

An insurrection led by Pueblo Indians broke out in January 1847.  They killed Governor Bent, rallied support among the small towns of northern New Mexico, and prepared for an attack on Santa Fe.  Col. Price, with some 500 soldiers and artillery, attacked the rebels with maximum force at Pueblo de Taos, February 3-5.  Price reported 150 Mexican and Pueblo Indians dead, and U.S. casualties of seven dead and forty-five wounded.  Over the next three months, trials were held and 22 Mexicans and five Pueblo Indians were hanged.  William B. Drescher, a U.S. soldier who witnessed the hangings, wrote in his memoirs. “You should have seen the poor wives of the Indians hung — heard their moans and observed their despair.”^[80]  The New Mexico territory thereafter remained securely in the hands of the Americans.

San Francisco harbor, 1846

The Polk administration made quick work of conquering Alta California, having prepared well in advance.  In June 1845, eleven months before the outbreak of war, he sent “secret and confidential” instructions to Commodore John Sloat, commander of U.S. naval forces in the Pacific:  “If you ascertain with certainty that Mexico has declared war against the United States, you will at once possess yourself of the port of Saint Francisco, and blockade and occupy such other ports as your force may permit.”  Sloat was thus prepared to act when he received word a year later that hostilities had commenced.  He took charge of Monterey on July 7, 1846, and San Francisco two days later, announcing, “Henceforth California will be a portion of the United States.”^[81]  As in New Mexico, Sloat told the Mexican people that the U.S. was not “an enemy” but a friend who would treat them with respect.

Bear Flag revolt in northern California

Prior to Sloat’s takeover of the port cities, some thirty Americans in Sonoma, north of San Francisco, initiated a revolt on June 14, 1846.  According to an account by one of the rebels, Robert Semple, the armed group woke up General Mariano Vallejo that morning, who inquired of the raggedy looking intruders, “To what happy circumstances shall I attribute the visit of so many exalted personages?”  One rebel replied, “We mean to establish our own government in California, and independent republic, and are under arms to support it.  You are under arrest, General.”^[82]  The rebels proclaimed the independent “Bear Flag Republic.”  The republic lasted only one week before John C. Frémont, an agent of Polk, arrived and took command of the rebellion in the name of the United States.  On July 15, Sloat transferred his command to Commodore Robert F. Stockton, who placed Frémont’s forces under his command.

General Scott and the occupation of middle Mexico

General Scott’s army traveled 260-mile inland from Veracruz to Mexico City (click to enlarge)

Scott needed to win a measure of acceptance from the Mexican people in order to minimize attacks on U.S. troops, secure food and supplies en route to Mexico City, and maintain law and order in the towns and cities under U.S. control.  Upon arriving in Tampico in mid-February 1847, Scott issued General Order No. 20, or Martial Law Order, which “made rape, murder, assault, robbery, desecration of churches, disruption of religious services, and destruction of private property court-martial offenses” for all persons, Mexican and American.  According to John Brown, “All accused offenders would be tried before a court made up of officers appointed by the commanding general.  The tribunals had the authority to determine innocence or guilt and to levy punishment, which included the lash, hard labor in ball and chain, imprisonment, branding, and even death.”^[84]

American forces bombard Veracruz

Bombardment in Veracruz, March 25, 1847

The American press was on hand to witness the affair.  George Kendall of the New Orleans Picayune watched the American bombardment with awe.  “The conflagration was certainly the most grand I have ever witnessed,” he wrote, as fires lit up the city.  The shelling continued the next morning, which Kendall called “tremendous.”  Only later, after walking through the wreckage, did Kendall consider the lethal effects of the barrage.  The city “has been torn all to pieces – the destruction is dreadful,” he wrote.  “It is certain that women, children and non-combatants have suffered the most.”^[87]  Kendall’s colleague at the New Orleans Delta, James Freaner, concurred, “The destruction of the city is most awful.  One half of it is destroyed.  Houses are blown to pieces and furniture scattered in every direction – the streets are torn up and the strongest buildings seriously damaged.”  The New York Spirit of the Times reported, “The Mexicans variously estimated their loss from 500 to 1000 killed and wounded; but all agree that the loss among the soldiery is comparatively small, and the destruction among the women and children is very great.”^[88]

Battle of Cerro Gordo, en route to Mexico City

As Scott’s forces regrouped and began their journey toward Mexico City, Santa Anna attempted to block Scott’s route at the strategic mountain pass of Cerro Gordo.  Santa Anna had assembled a force of 12,000 and spent a week fortifying his position.  His troops, however, were in a pitiful state, as half had marched more than 1,000 miles since the Battle of Buena Vista.  “They had suffered from hunger and heat, thirst and cold, storms and sickness, pestilence and snows,” according to Mexican authors.^[91]  The battle took place on April 17-18.  The Americans planned their strategy well.  On the second day, they routed the Mexican troops and captured 3,000 soldiers and officers along with artillery, ammunition, clothing, provisions, and a chest of money.  It was a devastating defeat for Santa Anna.  He retreated to Mexico City to organize the last valiant defense.

General Winfield Scott, portrait by George Catlin, c.1835

Scott was similarly intent on preventing depredations in other towns under U.S. control.  “For example,” writes the historian John C. Pinheiro, “when a mob of volunteers, regulars, and sailors robbed liquor stores, raped women, and burnt homes in a hamlet near Vera Cruz in March 1847, without a second thought Scott promptly arrested the men.”  In another case, a U.S. soldier who killed a Mexican woman at Jalapa was ordered hanged by a military tribunal.  Such enforcement signified a major improvement in curbing personal violence as compared to the American occupation in northeastern Mexico.  In April, Scott received instructions from Secretary of War Marcy to the effect that “the Army is to support itself by forced contributions levied upon the country, if at all possible.”  Like Taylor, Scott rejected this harsh option and continued to pay fair prices.^[93]

Mass hanging of San Patricios as the U.S. flag appeared over Chapultepec

On August 7, 1847, Scott began his move to take the capital city.  Santa Anna had assembled a defensive force estimated at 25,000 men.  The two armies clashed just south of the city in the battles of Contreras and Churubusco, August 18-20.  American tactics and artillery, coupled with a shortage of ammunition on the part of Mexican forces, enabled the Americans to prevail once again.  The San Patricio Battalion fought with desperation, expecting to be executed if captured.  U.S. forces suffered an estimated 1,000 casualties.  They took prisoner 4,000 Mexican troops, four generals, and 85 San Patricios, of whom 50 were later executed.  The two sides signed a temporary armistice on August 23 that allowed for an exchange of prisoners and stipulated that neither side undertake military maneuvers or build fortifications.  Peace talks were initiated but quickly broke down.  General Scott accused Santa Anna of violating the truce and hostilities resumed.

Mexican defense at Belén Gate, Mexico City

On the morning of September 14, a delegation of city leaders approached Scott’s headquarters under a flag of truce and surrendered the city.  Scott and his army then marched into the main plaza, raised the American flag, and declared victory, but the fighting was not over, as John Eisenhower describes:

The people of Mexico City did not roll over and play dead merely because Scott entered its gates in triumph.  Quite the contrary.  Santa Anna, to be sure, had retreated to Guadalupe Hidalgo, outside town, to await developments, but the crowds in the street were not so docile. . . . they clustered around the plaza and, supposedly provoked by the “haughtiness” of the Americans, became unruly. . . . an unidentified Mexican fired a shot.  Others followed . . . The [American] units formed ranks to fire, loaded their artillery pieces with canister, and began raking the streets.  Lookouts spotted buildings from which shots had been fired.  Solid shot blasted holes in the walls and angry soldiers poured through to kill and pillage.  Since most of the civilians were fighting only with stones, resistance in any one place melted away quickly.  By noon Scott’s men held all the critical points of the city, and mob violence subsided.  Mobs roamed the streets in the unlighted city that cold night, and dead bodies littered the cobblestones. . . . The violence became sporadic, with probably more civilians killed than soldiers.^[95]

The classic Mexican history of the war, Apuntes para la historia de la guerra entre México y los Estados Unidos (Notes for the history of the war between Mexico and the United States), does not refer to the Mexicans gathered as “mobs” but as patriotic citizens “acting in defense of their liberty,” even if their weapons consisted largely of “stones and billets of wood.”  The Americans responded with massive force, “bringing cannon, breaking down the doors, sacking houses, and committing a thousand other excesses. . . Horrible were the disasters that marked the occupation of Mexico. . . innocent people seized by an unbridled soldiery, attacked while disarmed, the doors of private dwellings broken, their houses sacked, and peaceful families slaughtered.”  That evening, the authors write:

The suffering families remained within their houses constantly in dread that the Americans would come to break open their homes, and perpetrate the most shameful crimes upon their persons. . . . Dead bodies lay scattered through the streets; many soldiers of the cavalry ran through the city, striking their swords against the walls, violating the doors of private houses and the stores of merchants, taking from the one the most precious goods and from the other eatables scarce among the inhabitants; for the fear of going forth to purchase them, at the very few shops open during the day, induced the quiet people to remain without food.^[96]

General Scott enters Mexico City

On September 17, three days after formal surrender of the city, Scott reissued his Martial Law Order, intended to prevent extrajudicial killings and atrocities, but it was less effective in Mexico City than in Veracruz.  “Volunteers, drunk on stolen liquor, committed rape and murdered unarmed civilians,” writes Amy Greenberg, “and soldiers were in turn murdered on a daily basis.”  The personal violence of the American occupation was not immediately captured in news reports, which emphasized the great victory of U.S. forces over the larger Mexican army.  George Kendall of the New Orleans Picayune wrote, excitedly, “Another victory, glorious in its results and which has thrown additional luster upon the American arms, has been achieved today by the army under General Scott – the proud capital of Mexico has fallen into the power of a mere handful of men compared with the immense odds arrayed against them, and Santa Anna, instead of shedding his blood as he promised, is wandering with the remnant of his army no one knows whither.”^[97]

Death of Capt. Walker in the battle of Huamantla

Santa Anna, meanwhile, had rounded up the remnants of his army and was besieging Pueblo, attempting to cut off American supply lines.  Brig. Gen. Joseph Lane led a relief column to disperse Santa Anna’s forces.  A skirmish took place near the town of Huamantla on October 9, 1847, which resulted in the death of Captain Samuel Walker of the Texas Rangers.  Lane then ordered his men to “avenge the death of the gallant Walker,” according to a report by Lt. William D. Wilkins.  The American troops pillaged liquor stores, got drunk, and committed numerous atrocities.  According to the historian John Brown, “Lane’s troops murdered dozens of Mexicans, raped scores of women, and burned many homes.  For the only time, Scott’s troops lost all control.”  No one was punished, as Scott needed every soldier to keep the guerrilla war in check.^[99]  As for the mercurial Santa Anna, he was ordered to appear before a Mexican military court of inquiry, but abandoned his command instead and headed for the Guatemalan border.  It would be five years before he returned to power.

IV.  Debate and opposition to the war within the United States

Horace Greeley, editor and Whig Party activist, 1961 commemorative stamp

Many citizens did hold meetings, speak out, and act against the war.  Yet more were initially roused by the war spirit.  That excitement, however, subsided rather quickly.  Within six months, enlistments plummeted, and by the end of the 1847, antiwar sentiment was at its height – an oddity considering the success of American military forces in central Mexico.

In the same address, Polk took aim at the opponents of the war, charging them with giving “aid and comfort” to the enemy:

The war has been represented as unjust and unnecessary and as one of aggression on our part upon a weak and injured enemy. Such erroneous views, though entertained by but few, have been widely and extensively circulated, not only at home, but have been spread throughout Mexico and the whole world. A more effectual means could not have been devised to encourage the enemy and protract the war than to advocate and adhere to their cause, and thus give them “aid and comfort.”^[102]

President Polk himself did not engage in extreme defamation of the war critics, in part because some were from his own party, but his allies and the pro-administration press were inclined to push the matter, labeling the war critics “Mexican Whigs.”  The insinuation of treason was strongly resented by those who deemed themselves patriots of the first order.  Theodore Parker, a Boston Unitarian minister, orator, abolitionist, and social reformer, rebutted the charge of treason in a speech on February 4, 1847:

Your President tells us it is treason to talk so!  Treason, is it?  Treason to discuss a war which the government made, and which the people are made to pay for?  If it be treason to speak against the war, what was it to make the war, to ask for 50,000 men and $74,000,000 for the war?  Why, if the people cannot discuss the war they have got to fight and to pay for, who under heaven can?  Whose business is it, if it is not yours and mine?  If my country is in the wrong, and I know it, and hold my peace, then I am guilty of treason, moral treason. . . . Treason is it, to show that this war is wrong and wicked?^[103]

Parker presents an interesting case among the dissenters.  He was both an expansionist and a racist, in keeping with the times.  He expected that the United States would one day “possess the whole of the continent,” in his words.  “But this may be had fairly; with no injustice to any one; by the steady advance of a superior race, with superior ideas and a better civilization; by commerce, trade, arts; by being better than Mexico, wiser, humaner, more free and manly.”  Parker was thus not opposed to continental expansion, but he differed with Polk and company over the means to this end.  Parker viewed Mexicans as “a wretched people,” but he acknowledged that Mexicans had “abolished slavery” and did not “covet the lands of their neighbors.”  However “inferior” to their northern neighbors, the Mexicans did not deserve to be invaded and robbed of their territory.^[104]

Judge William Jay, APS president, 1848-58

Among the organized opposition to the war was the American Peace Society (APS), a coalition of state peace societies formed in 1828.  The group included women as well as men and was primarily active in northern states.  The group was not pacifist, but viewed war as an outdated institution and called for a “Congress of Nations,” an idea that later came to fruition in the League of Nations and United Nations.  William Jay, a New York jurist who became president of the APS in 1848, argued that “at least 23 different international controversies (including a recent Anglo-American quarrel over Maine’s boundary) had been submitted successfully to arbitration in the generation before 1840,” according to the historian Charles DeBenedetti.  APS members petitioned the Polk administration to recall American troops from Mexico and to resolve outstanding issues through mediation and negotiation.  The APS publication, Advocate of Peace, printed speeches, petitions, sermons, and poems against the war along with “eyewitness accounts of the degradation of army life and the horrors of battle.”^[105]  Jay and others argued that, while immoral personal conduct was difficult to control in any war, it was all the more likely in a war whose goals were unjust and inhumane.  How could the U.S. Army prevent its soldiers from committing abuses when the whole point of the war was to rob Mexico at the point of a gun?

Frederick Douglass, abolitionist orator and editor of the North Star

Antiwar arguments concerning the expansion of slavery, in contrast, were distinctly northern.  Northern abolitionists such as Frederick Douglass, William Lloyd Garrison, and former president John Quincy Adams were among the most vociferous and consistent opponents of the war.  Douglass connected the slavery issue to racism, writing in his newspaper, North Star, “Mexico seems a doomed victim to Anglo Saxon cupidity and love of domination.”^[107]  Abolitionists also raised the argument that the slave South was intent on controlling the destiny of the nation, to the detriment of the free states.  This argument gained wide attention in the North, beyond abolitionist circles.  The Senate at the time was evenly divided between free and slave states.  Northerners saw evidence of a “slave power” conspiracy in the earlier actions of the Texas Republic, which converted a liberated region into slave territory and made extensive claims on Mexican lands in the hope of extending slavery to the Pacific coast.  Fear of the “slave power” prompted Rep. David Wilmot of Pennsylvania to introduce an amendment in the House on August 8, 1846, calling for a ban on slavery in any territories acquired from Mexico.  The Wilmot Proviso, as it was called, was approved in the House but failed in the Senate.  President Polk opposed the measure but refused to say how new territories should be established, thereby inviting speculation and apprehension.

In April 1847, the Massachusetts legislature passed a resolution that combined all of the main arguments against the war and called on all citizens “to join in efforts to arrest this gigantic crime”:

Resolved, That the present war with Mexico has its primary origin in the unconstitutional annexation to the United States of the foreign state of Texas while the same was still at war with Mexico; that it was unconstitutionally commenced by the order of the President, to General Taylor, to take military possession of territory in dispute between the United States and Mexico, and in the occupation of Mexico; and that it is now waged ingloriously–by a powerful nation against a weak neighbor–unnecessarily and without just cause, at immense cost of treasure and life, for the dismemberment of Mexico, and for the conquest of a portion of her territory, from which slavery has already been excluded, with the triple object of extending slavery, of strengthening the “Slave Power,” and of obtaining the control of the Free States, under the Constitution of the United States.

Resolved, That such a war of conquest, so hateful in its objects, so wanton, unjust, and unconstitutional in its origin and character, must be regarded as a war against freedom, against humanity, against justice, against the Union, against the Constitution, and against the Free States; and that a regard for the true interests and the highest honor of the country, not less than the impulses of Christian duty, should arouse all good citizens to join in efforts to arrest this gigantic crime, by withholding supplies, or other voluntary contributions, for its further prosecution; by calling for the withdrawal of our army within the established limits of the United States; and in every just way aiding the country to retreat from the disgraceful position of aggression which it now occupies towards a weak, distracted neighbor and sister republic.^[108]

Henry David Thoreau

One Massachusetts resident, Henry David Thoreau, had already taken action.  In July 1846 he refused to pay his poll taxes in symbolic protest against the war, an action that landed him in jail for a night.  Two years later, he gave a lecture on “Resistance to Civil Government,” in which he argued in principle that citizens should disobey their government when it engages in evil policies or actions.  Such was the case in the Mexican War, he said, for “when a sixth of the population of a nation which has undertaken to be the refuge of liberty are slaves, and a whole country [Mexico] is unjustly overrun and conquered by a foreign army, and subjected to military law, I think that it is not too soon for honest men to rebel and revolutionize.”^[109]

The Whig Party

John Quincy Adams

Most Whigs members of Congress also praised American soldiers and officers in the field, the most prominent of whom were Whigs – Generals Zachary Taylor and Winfield Scott.  Former president John Quincy Adams was one of the exceptions.  He was about to speak to the issue when he suffered a fatal stroke on February 21, 1848.  According to the historian William Earl Weeks:

This occurred while he was rising to oppose a resolution paying tribute to officers who had served in the 1846-48 Mexican-American War. Adams reasoned that it was wrong to honor soldiers who fought for a dishonorable cause, in this case, to expand the domain of slavery as he saw it. He literally keeled over while standing for the principle that it is wrong for the nation to honor its veterans of unjust wars, that service in the military does not mean one can check one’s conscience at the door, and that as individuals we are always responsible for our actions.^[111]

Whig members of Congress maintained a steady stream of criticism of the war.  Following the president’s Second Annual Message, Rep. Charles Hudson of Massachusetts spoke on December 16, 1846:  “The message, Mr. Chairman, declares ‘that the exiting war with Mexico was neither desired nor provoked by the United States; on the contrary, all honorable means were resorted to avert it!’  This declaration I pronounce an absolute untruth; and it will be the object of my remarks to sustain this position.  I believe the President, in making that declaration, has made a statement which is not supported, but is in reality contradicted, by the facts in the case.”^[112]  In February 1847, Whigs united on a proposal to curb the president’s territorial ambitions and bring the war to a close.  Introduced by Representative Alexander Stephens and Senator John Berrien, both from Georgia, the proposal stated that “the war with Mexico ought not be prosecuted by this Government with any view to the dismemberment of that republic, or to the acquisition, by conquest, of any portion of her territory.”^[113]  The Democrats once again voted the measure down.

Whig party leader Henry Clay

Later that year, the venerated Whig leader and elder statesman Henry Clay helped catalyze a new surge of peace activism.  Speaking to a large gathering in Lexington, Kentucky, on November 13, 1847, he denounced Polk’s aggressive war and its unconstitutional beginnings, and in the seventh of eight resolutions, resolved that the United States must not “acquire any foreign territory whatever, for the purpose of propagating Slavery, or of introducing slaves from the United States into such foreign territory.”  Clay’s public statement on this issue led future Whig leaders such as Zachary Taylor to similarly oppose the expansion of slavery, as did the Republican Party in the 1850s.  Clay also spoke of the great tragedy of war, his son’s recent death no doubt weighing on his mind:

In the sacrifice of human life, and in the waste of human treasure in its losses and in its burthens, it [war] affects both belligerent nations; and its sad effects of mangled bodies, of death, and of desolation, endure long after its thunders are hushed in peace.  War unhinges society, disturbs its peaceful and regular industry, and scatters poisonous seeds of disease and immorality which continue to germinate and diffuse their baneful influence long after it has ceased.  Dazzling by its glitter, pomp and pageantry, it begets a spirit of wild adventure and romantic enterprise, and often disqualifies those who embark in it, after their return from the bloody fields of battle, from engaging in the industrious and peaceful vocations of life.^[114]

A journalist from the Milwaukee Sentinel and Gazette wrote:  “It may be that Mr. Clay has uttered the truth too boldly for popularity at the moment.  But succeeding years will increase the conviction that a truer and bolder man never stood forward to enlighten and guide his countrymen, even against their will.”^[115]

The All of Mexico movement

V.  The Treaty of Guadalupe Hidalgo

Nicholas Trist

The American negotiator in Mexico City, Nicholas P. Trist, waited patiently, having arrived in Veracruz on May 6 and begun negotiations in early September.  Prior to his appointment, Trist had been the Chief Clerk of the State Department, second in command to the secretary of state.  As a young man he had been tutored by Thomas Jefferson and married Jefferson’s granddaughter, Virginia.  He was fluent in Spanish, well-versed in law, and had served as the American consul in Havana, Cuba.  He thus appeared to be a good choice for negotiating a difficult treaty.  He was also, like Polk, a Democrat, a plantation slaveholder, and a speculator in land.  “But as it was,” writes Amy Greenberg, “Polk never got to know Nicholas Trist well enough to recognize two traits that Jefferson left to his son-in-law:  the conviction that he was smarter than almost everyone else, and an innate distrust of war.”  She adds:

The distrust of war was perhaps more his grandmother’s doing than Jefferson’s. . . . “I would as soon hear of your turning Highway man as to join any army, from ambitious motives,” she told him.  “War is at best a horrid calamity and those who wage war for the purpose of subjugating nations to their will are guilty of a heinous crime.”  She reminded “Dear Nicholas” that “when the hour arrives that you must quit this World let not your conscience upbraid you with having done any thing to dishonor humanity.”^[124]

Trist’s conscience was, in fact, disturbed by the war.  Following the ratification of the peace treaty, Trist remarked, “Could those Mexicans have seen into my heart at that moment, they would have known that my feeling of shame as an American was far stronger than theirs could be as Mexicans.  For though it would not have done for me to say so there, that was a thing for every right minded American to be ashamed of, and I was ashamed of it, most cordially ashamed of it.”^[125]

“The peace treaty has been signed: Mexico has lost half its territory”

Trist, despite his lack of official credentials, negotiated an agreement with a special commission led by Don Bernardo Couto, Don Miguel Atristain, and Don Luis Gonzaga Cuevas.  The agreement essentially followed Polk’s original instructions to Trist.  The Treaty of Guadalupe Hidalgo (named for a small town near Mexico City) was signed on February 2, 1848, and sent to Washington.

If unhappily any disagreement should hereafter arise between the Governments of the two republics, whether with respect to the interpretation of any stipulation in this treaty, or with respect to any other particular concerning the political or commercial relations of the two nations, the said Governments, in the name of those nations, do promise to each other that they will endeavour, in the most sincere and earnest manner, to settle the differences so arising, and to preserve the state of peace and friendship in which the two countries are now placing themselves, using, for this end, mutual representations and pacific negotiations.^[130]

VI.  Legacies, lessons, and perspectives on the war

Ancient Greek historian and philosopher Thucydides

These words, written over 2,400 years ago by the Athenian historian Thucydides, suggest that war negates our ability to understand and empathize with other human beings deemed the “enemy.”  Conversely, once the passions of war are doused or burn out, the recognition of the other’s human qualities and sensibilities may be restored.  This was the intent of the peace agreement, “to preserve the state of peace and friendship.”

Yet it was easier for Americans to forgive and forget than for Mexicans who had endured the American invasion and occupation.  Mexicans held Americans responsible for the war and its attendant sufferings.  As the Mexican newspaper, El Republicano, wrote on October 23, 1846:

A government … that starts a war without a legitimate motive is responsible for all its evils and horrors. The bloodshed, the grief of families, the pillaging, the destruction, the violence, the fires, and its works and its crimes….  Such is the case of the U.S. Government, for having initiated the unjust war it is waging against us today.^[132]

Many U.S. citizens also believed that the war was unjust and unnecessary.  Their arguments and opposition to aggressive expansionism and slavery carried over into the next decade, helping to thwart American expansionist designs on Cuba and Nicaragua.  Thoreau’s essay on Civil Disobedience became a foundational text for later nonviolent change movements.  It had a profound effect on Mohandas Gandhi, who organized social justice campaigns in South Africa and Great Britain.  Gandhi, in turn, deeply influenced Martin Luther King, Jr., who led nonviolent civil disobedience campaigns in the American South.  King’s civil rights movement, in turn, inspired nonviolent revolutions in Eastern Europe against oppressive governments in the late 1980s.  The advocates of peace and justice furthermore helped establish “just war” and humanitarian principles in international institutions and law – via the Charter of the United Nations, Geneva Conventions of 1949, and human rights courts.

Historical interpretations and perspectives

Nathan Brooks, in A Complete History of the Mexican War (1849) justified the Polk administration’s actions as “defensive” and claimed that the war had the “most beneficial consequences” for both Americans and Mexicans.  The benefits for Americans included “the rapid settlement of the newly-acquired territory,” a revitalization of “manly vigour,” and “a prominent rank among the nations of the earth,” owing to the fact that the U.S. had successfully invaded a foreign country.  The 80,000 Mexicans who became Americans by virtue of the ceded territory were said to benefit by “the example of their northern neighbours, who may settle among them, . . . [and] raise them from their present ignorance and degradation, to all the blessings of rational liberty and a higher civilization.”  Even Mexico was said to benefit from the war, as “she will at length rise to an appreciation of real liberty, learn that her true policy is industry and peace, and, beating her ‘swords into ploughshares, and her spears into pruning-hooks,’ find her chief wealth and happiness in peaceful, health-inspiring toil.  Nor is this all,” Brooks continued:

The light of liberty and civilization, from where our flag is now planted on the shores of the Pacific, will illumine not only the adjacent countries, but the far-off islands of the watery waste.  From the bay of San Francisco, our white- winged ships will visit the shores of Asia and Africa, and each green isle that gems the Southern Ocean, freighted for their heathen inhabitants not merely with perishable merchandise, but the ‘true riches,’ civilization, and the knowledge of the one God, causing the ‘isles to be glad,’ and the ‘desert to smile and blossom as the rose.’ ^[136]

In the view of many historians, the successor to Smith’s voluminous study was David Pletcher’s heavily footnoted work, The Diplomacy of Annexation: Texas, Oregon, and the Mexican War (1973).  Pletcher evaluated President Polk’s foreign policies on the basis of whether they served American national interests.  He thus continued Smith’s nationalistic framing of the war but, unlike Smith, was hesitant to embrace Polk’s course of action and was more respectful of contrary views.  Pletcher drew up a balance sheet of U.S. gains and losses.  The gains were primarily the acquisition of “more than 1,200,000 square miles of territory” and “the increasing respect of Europeans” presumably impressed by America’s “show of power.”

Against these American gains of territory and prestige, however, the appraising historian must charge certain losses.  Some of these were the familiar costs of all wars: about 12,800 men dead out of 90,000 under arms and about $100 million in expenses, to which might be added the $15 million paid to Mexico under the peace treaty.  The families and friends of the dead soldiers were the chief sufferers, for the growing nation hardly felt the expenditure of men and money.

There were intangible deficits as well.  One was the reaction in Latin America to the nation’s “overblown chauvinism with strong hints of militarism and racism,” leading to a negative “stereotype” of the U.S. as “the Colossus of the North.”  The most “alarming” result, however, was the widening division in the U.S. over whether the new territories should be free or slave.  All in all, Pletcher gives the impression that the benefits outweigh the deficits, but he allows for the possibility that “later generations might reasonably complain that he [Polk] served his country ill by paying an unnecessarily high price in money, in lives, and in national disunity.”  In fact, past generations came to this conclusion, beginning with Mr. Polk’s many critics.  In his concluding chapter, Pletcher asked the question, “Was the war, in fact, necessary?”  His exploration of this question, however, is confined to the framework of what’s good for the United States; hence, the choice comes down to whether the U.S. should obtain Mexican territories quickly by force or more slowly by population infiltration and subversion.^[142]

Historian Josefina Zoraida Vázquez

Mexican historian Josefina Zoraida Vázquez found much to criticize in a scholarly review of Pletcher’s study.  While praising Pletcher’s grasp of international diplomacy, she cited a lack of understanding and inclusion of Mexican experiences and perspectives as well as crude stereotypes.  Vazquez took issue with Pletcher’s summary judgment that Mexico was in a state of “confusion, mismanagement and humiliation” in the early 1840s, arguing that Pletcher failed to identify the experiences and conditions that gave rise to Mexico’s troubles, including three international wars.  Regarding Polk’s territorial ambitions, Vazquez found Pletcher’s analysis to be almost a cover-up, arguing that Pletcher exonerated Polk of any conspiracy or provocation, and took at face value Polk’s claim that his aggressive actions were designed merely to allow the U.S. to negotiate from a position of strength.^[143]

Taking stock of the long train of historical writing on the U.S.-Mexican War, the American military historian John Eisenhower, son of President Dwight D. Eisenhower, wrote in So Far from God: The U.S. War with Mexico, 1846-1848 (1989), “without a doubt, the preponderance of American opinion has agreed with [Ulysses S.] Grant that the United States treated Mexico unjustly.”  Indeed, Grant’s view of the war was incorporated into the title of Amy S. Greenberg’s engaging study, A Wicked War: Polk, Clay, Lincoln, and the 1846 U.S. Invasion of Mexico (2012).  Yet Eisenhower also indicated that “excessive” remorse is not necessary, since, in his view, if the United States had not taken Mexico’s northern territories, some other power “would inevitably” have done so, given Mexico’s military weakness and political instability:

To the student of today the fate of Mexico is sad, for the Mexicans were victims of both their history and U.S. expansionism.  But that sadness need not be exacerbated by excessive shame for the conduct of the United States, because Mexico’s disorganization, corruption, and weakness created a power vacuum that would inevitably have been filled by some predator – if not the United States, then Britain, less likely France, and even, remotely, Russia.  American haste to occupy California, for example, was prompted more by fear of British action than by concern of what Mexico would do.  After all, the United States and Britain were threatening war over the Oregon territory just north of California.  Mexico’s weakness stemmed from nearly three centuries of autocratic Spanish rule and from its own devastating war of independence, not from the actions of the United States.^[144]

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