As had been the case a decade earlier in Texas, “Manifest Destiny” formed the leitmotif of the Mexican–American War. In his biography of Polk, Eugene McCormac observed:
Determined from the beginning to add California and New Mexico to our national domain, he pursued his object with a dogged persistence which neither opposition nor denunciation could weaken. Whatever may be thought of his motives or his methods, to him is due the credit (or censure, if you please) of extending to the Pacific the boundaries of the United States.
The Mexican press limited the possible actions of Mexico’s leaders by urging war on them and whipping up public sentiment to favor war. Mexicans’ failure to accurately assess the relative military strength of the United States and Mexico impaired their decision-making ability. Finally, many in Mexico felt that if Mexico did not take a strong stance against its northern neighbor, the United States would continue to press claims forever, nibbling away at Mexican territory until the nation ceased to exist.
Given that the United States had long supply lines, a pre-industrial economy, and a small standing army, and that it was forced to attack the strong defensive position offered by the Sierra Madre Oriental, it is worth considering why the United States triumphed over Mexico. The U.S. victory amazed European observers. A British journalist commented, “There must be some mystery—some leading cause, imperfectly understood on our side of the Atlantic.”
Factors contributing to the U.S. victory include:
■ The U.S. population at the time of the war consisted of 17 million whites and 3 million slaves, more than double the number of Mexicans. This enabled the United States to draw on a much larger population for soldiers and war production.
■ African Americans formed a significant element of the U.S. presence in Mexico, performing labor in camp and serving white soldiers. The Mexican–American War is the only U.S. war in which African Americans were not mobilized as combatants—an indicator of the racial sensitivities of the time. Far outweighing African Americans’ contribution in Mexico, black slaves in the United States produced food and cotton for military uniforms and for export.
■ The United States made extensive use of light “flying” artillery that could be moved rapidly, keeping up with the troops and advancing to fire on enemy positions. Artillery officers were permitted to move and fire without having to wait for orders from a central command. The U.S. artillery played a crucial role in several battles, such as those as Palo Alto, Monterrey, and Veracruz. At Buena Vista, General John Wool stated, “Without our artillery we would not have maintained our position a single hour.”
■ The smooth-bore muskets that were the standard U.S. infantry weapon were among the world’s most advanced shoulder weapons. The milling machines used in their manufacture produced interchangeable parts and uniform barrel diameter. U.S. muskets had a range of 220 yards, considerably greater than the hundred-yard range of the Mexicans’ muskets.
■ By the time of the Mexican–American War, the majority of the lieutenants and captains were West Point graduates. Years of campaigning against elusive Indian guerrillas on the western frontier accustomed these officers to rapid, decentralized decision-making. Such officers were especially valuable when U.S. forces were operating in small units, as at Resaca de la Palma. After the war, Scott commented:
I give it as my fixed opinion that but for our graduated cadets the war between the United States and Mexico might, and probably would, have lasted some four or five years, with, in its first half, more defeats than victories falling to our share, whereas in two campaigns we conquered a great country and a peace without the loss of a single battle or skirmish.
■ The élan of the all-volunteer U.S. force was crucial. Many existing militia units volunteered en masse, reinforcing camaraderie. Initial American victories lifted spirits and additional triumphs kept them high. This élan and patriotism was evident in one officer who saw the U.S. flag at Monterrey and commented, “A glow of honest pride lit up my face, and I thanked God I was an American, and that he had endowed my own country with so much to love and venerate.”
■ Even though some Americans opposed the war, the United States was much more united than Mexico. The desire to acquire California was a generally shared goal, just as expansion into the Mississippi Valley had been a generation earlier. Herman Melville described the pro-war feeling in a small New York town: “People here are all in a state of delirium about the Mexican War. A military ardor pervades all ranks … and ’prentice boys are running off to the wars by scores.—Nothing is talked of but the ‘Halls of the Montezumas.’”
■ The U.S. economy, unlike the Mexican economy, which had yet to recover ground lost during the struggle for independence, was beginning its industrialization. The United States could achieve what, for the times, were prodigious logistical feats. For example, within a four-month period, forty-nine ten-inch mortars and 50,000 shells were ordered, manufactured, and transported to Veracruz.
A number of factors contributed to the Mexican loss:
■ The Mexican population of seven million was substantially smaller than the U.S. population. Only a small proportion of Mexico’s population was mobilized, some 70,000 out of 7 million, or 1 percent. This contrasts with the U.S. Civil War in which roughly 3 million, or 10 percent of the population, were mobilized for the Union and Confederate armies.
■ Mexican statesmen failed to see in time that the United States constituted a threat to Mexico. As late as 1825, the Mexican government convened a special commission to advise on developing California. It warned not of danger from the United States but from Russia. Even the normally perceptive Humboldt wrote in the first decade of the nineteenth century that
the principles of wisdom and moderation by which the government of the United States is animated, lead us to hope that a friendly arrangement will soon fix the limits between the two nations, who both possess more ground than they can possibly cultivate.
■ Some Mexicans did see the danger posed by the United States before war broke out. For example, former President Valentín Gómez Farías wrote in 1843 that Texas was the key, which if it should fall into American hands, would unlock the last barrier to the rest of northern Mexico. By taking this “giant step” toward California, he wrote, the United States would be extended “from sea to sea” and Mexico’s hopes for a prosperous future would be gone. By then it was too late to save California.
■ The frequent changes in government in the mid-1840s undermined the government’s already weak financial structure. The U.S. occupation of the Veracruz, Tampico, and Matamoros customs houses further impoverished the government.
■ The ever present possibility of a coup made presidents keep one eye on the United States and the other on possible rivals. The most serious internal conflict, known as the Revolt of the Polkos, occurred just before the invasion of Veracruz when conservatives rebelled against liberals in the capital. Rather than rushing to defend the port, Mexicans engaged in an artillery duel in downtown Mexico City. The revolt was triggered by liberal Acting President Gómez Farías authorizing the government to confiscate Church property to finance the war.
■ The actions of individual Mexican states also weakened the war effort. Yucatán declared itself independent on January 1, 1846. This renegade state not only failed to contribute to the war effort but sold supplies to U.S. naval forces blockading Veracruz before the invasion. California, Tabasco, Sinaloa, and Chihuahua were unable to contribute to the national war effort because they were fighting what amounted to internal civil wars. By default, much of the defense burden fell on the individual state being invaded. Puebla failed to accept this defense burden, and the State of Mexico, which U.S. forces had to pass through to enter Mexico City, declared itself to be neutral. Many state governors were reluctant to raise militia units due to the long-standing perception that military commanders were abusive and authoritarian. Conservative governors were reluctant to see militia units recruit politically unreliable members of the lower classes. The Mexico City municipal government opposed attempts to fortify the city.
■ Political, class, and racial divisions hampered the war effort. In 1848, the newspaper El Siglo XIX commented:
The forces of disintegration—formerly civil strife and more recently foreign war—have been building up in our country. They have gathered so much force, are so numerous, and are so palpable that at first glance one can doubt if our republic is really a society rather than simply a gathering of men without bonds, rights, and duties.
■ Many wealthy Mexicans not only failed to contribute to the war effort but actually welcomed the invaders. Often merchants preferred Scott to Santa Anna and his forced loans. Santa Anna complained that the wealthy went into hiding as U.S. troops approached Mexico City, so they could avoid contributing to its defense. Certainly the sight of the rich attending the opera and bullfights did nothing to encourage the defenders of Mexico City, who ate poorly and were practically dressed in rags.
■ The wealthy and the Church wanted to maintain their properties and prerogatives. The United States made it clear that none of these interests would be jeopardized. After taking Veracruz, Scott published a manifesto declaring that Americans were friends of the Mexicans and that the Catholic Church and property rights would be respected. He and his staff attended Mass at the Cathedral in full dress uniform. He ordered his men to salute priests. President Polk requested that Catholic bishops in the United States inform their Mexican counterparts that the United States would respect the Church.
■ Unlike slaves in America, Mexican Indians, roughly half the population, produced little surplus that could support the war effort. They had little in common with the rest of Mexico and little sense of belonging to a “nation.” Taking advantage of the national crisis to advance their own causes, indigenous people staged widespread uprisings in the central and southern regions following the U.S. invasion. In northern Veracruz, Indians under pressure from encroaching cattlemen rose up, burning towns and haciendas. Hacendado Manuel Soto wrote, “Blood ran in torrents, and for ten months the Huasteca [region of Veracruz] was the stage for the most horrible scenes.” Suppressing such uprisings diverted men and arms away from fighting Americans.
■ Prolonged conflict with independent Indian groups such as the Apache had left large areas of northern Mexico unable and unwilling to resist the U.S. army. American troops frequently encountered abandoned homes, overgrown fields, and hastily finished graves—a result of Indian raids—in the parts of northern Mexico they occupied. Prior to the Battle of Buena Vista, the states of Chihuahua, Durango, and Zacatecas ordered soldiers to remain at home to protect against Indian raids.
■ The civilian population frequently reacted as if the war was being waged by two foreign powers. U.S. officers and Mexican landowners frequently fraternized. Other landowners, such as the Sánchez Navarro family in Coahuila, sold massive amounts of livestock, corn, and wheat to the U.S. army. To insure that the U.S. forces did not antagonize landowners, Generals Scott and Taylor insisted that all food and supplies needed by U.S. troops were paid for in voluntary, negotiated sales. Other Mexicans served U.S. troops as guides, teamsters, and spies and supplied them with mules, cattle, and corn.
■ The army reflected the chronic financial problems of early nineteenth-century Mexican governments. The lack of finances resulted in an army that was poorly equipped at the outbreak of hostilities and made it difficult to amass war matériel later on.
■ The professional army that defended Mexico reflected Mexican society as a whole. The army was poorly led, since individuals with little military training used bribes or political influence to obtain leadership positions. The officer corps was conservative and elitist. Of the 137 most senior officers, all but about twenty had fought on the Spanish side in the independence struggle. Changes in government generally resulted in changes in the army’s command structure. These repeated personnel shifts impaired fighting ability. Mexico’s bloated army had 24,000 officers commanding 20,000 enlisted men. The British ambassador wrote home in 1846 that the army was “the worst perhaps to be found in any part of the world.” Zeh, while marching on Mexico City, commented, “The enemy cavalry now had a marvelous opportunity to capture our generalissimo; but to do this required courage and a spirit of daring-do which, fortunately, they lacked.”
■ Morale among Mexican troops was low, since they were often impressed or taken from prisons. They received little training and, as a result, could not perform tactical maneuvers in large groups. Historian Josefina Vázquez described the army defending Mexico as
a ghost comprised of untrained conscripts who deserted as soon as the opportunity presented itself, and led by officers who dedicated themselves to politics. The cavalry and artillery, which had acquired a certain fame, had declined due to the lack of funds and failure to maintain proper levels of enlistment.
■ Waddy Thompson, the U.S. ambassador to Mexico from 1842 to 1844, noted that Mexican recruitment consisted mainly of capturing Indians, of whom no more than one in ten had ever seen a gun and not one in a hundred had fired one.
■ The effectiveness of Mexican cannons was limited by their being of a variety of calibers and by poor logistics. The solid shot used by Mexicans was less effective than the grape and canister shot used by Americans. Mexican muskets had been purchased from British stocks after they had been declared obsolete and often unserviceable. Zeh commented that after Cerro Gordo, “The captured muskets usually were collected into huge piles and set afire, because they were of no value.”
■ Mexican officers tended to view battles like chess games. They expected events to unfold within a clearly defined area. The Americans would repeatedly extend the limits of the battlefield, and win. This occurred at Resaca de la Palma, Cerro Gordo, and Contreras.
■ Mexican forces repeatedly withdrew before they were attacked. The list of such abandoned positions includes Matamoros, Tampico, Jalapa, Mazatlán, Tucson, El Paso, Santa Fe, and Chihuahua City. No military force existed in other cities such as Puebla. Others, such as Veracruz, Monterrey, and Mexico City, were defended for a time, and then surrendered. The fortress at Perote was abandoned along with a sizable amount of war matériel. A more determined defense would have increased the number of U.S. casualties, thus possibly undermining American support for the war.
■ Guerrilla warfare might also have defeated the United States. However, Santa Anna opposed a guerrilla strategy, feeling he could win on the battlefield. The wealthy opposed guerrilla warfare since the resulting disruption and social mobilization would be prejudicial to their interests. This, and the lack of a credible leader, prevented the creation a strong guerrilla force comparable to the force opposing Maximilian in the 1860s. The most serious action by irregulars was an attack on a supply train between the Rio Grande and Monterrey. In that attack, forty to fifty teamsters were killed, and 110 wagons and 300 pack mules were captured. Taylor referred to that attack as “an atrocious barbarism unprecedented in the existing war.”
■ Scott did his best to stamp out any outbreak of guerrilla warfare. During his six-year struggle against the Seminole, he had learned how hard it was to suppress a full-scale guerrilla insurrection. He ordered the summary execution of partisans and the destruction of villages supporting them. In addition, he held local mayors responsible for capturing and turning over to Americans anyone killing or robbing U.S. soldiers. Mayors who failed to capture such attackers faced heavy fines. To avoid antagonizing Mexicans, Scott also took special care to see that his forces avoided the repeated atrocities committed by some of Taylor’s forces.
■ Scott commented on these atrocities:
Our militia & volunteers, if a tenth of what is said to be true, have committed atrocities—horrors—in Mexico, sufficient to make Heaven weep, & every American, of Christian morals blush for his country. Murder, robbery & rape on mothers and daughters, in the presence of the tied-up males of the families, have been common all along the Rio Grande.
■ Many of Mexico’s problems resulted from its failure to have formed a national consciousness in the quarter century after independence. In 1848, statesman Mariano Otero commented, “There has not been, nor could there have been a national spirit, for there is no nation.”
To this date, Mexicans resent the loss of roughly 40 percent of “their” territory. However, just as was the case with the Adams–Onís Treaty, those most affected by the Treaty of Guadalupe Hidalgo were not the roughly 85,000 Hispanics on land ceded to the United States but the 160,000 Indians whose ancestral lands passed to U.S. control without their having been consulted.
In Mexico, the war was a painful but perhaps necessary shock to the nation, provoking self-examination. The questions raised by the war shaped a new generation and led to a consolidated state and increased nationalism, evident in the 1860s during the struggle against Maximilian. In the aftermath of the war, the dominance of the army, the Church, and the hacendados began to be questioned more strongly than ever before.
For most of the twentieth century, the Mexican Revolution of 1910–1917 overshadowed the Mexican–American War. However, by the end of the century the effects of the Revolution had largely run their course. The results of the Mexican–American War, in contrast, remain glaringly apparent. The four states—California, Arizona, New Mexico, and Texas—that form the bulk of the territory lost to the United States had a GDP almost four times that of Mexico in 2000.