The war between the United States and Mexico, which lasted for less than two years, resulted in the United States gaining a huge swath of territory from the defeated Mexicans. Its origins were based in part on a dispute about the proper boundary between the two nations and the United States’s annexation of Texas, formerly a state in the Republic of Mexico, in 1845. Texas had broken away from Mexico in 1836, defeating the Mexican army after the siege at The Alamo and establishing itself as a republic in its own right. American president Andrew Jackson of Tennessee, where many Texans were originally from, immediately recognized Texas, although Mexico did not. Soon thereafter, Texas applied for statehood; most Texans had migrated from the United States, and many of them desired to join the new republic to their former country. However, new president Martin Van Buren, a northerner, was cool to the idea, believing correctly that northern states might object to admitting another state that permitted slavery, as Texas did. The United States therefore passed on its first opportunity to admit Texas into the Union.
When the Whig Party, which was increasingly opposed to the expansion of slavery, elected its first president, William Henry Harrison, in 1840, it looked as though any U. S. annexation of Texas would be postponed for some time. However, Harrison died soon after taking office and was replaced by Vice President John Tyler, a southerner and former Democrat. In the United States at that time was a growing belief in the idea of Manifest Destiny, which held that the nation was destined to rule all of North America, including much of Mexico. This idea was tinged with racial and cultural superiority, with some Americans believing that Anglo-Saxons were entitled to lands that the darker-skinned (and Catholic) Mexicans were not using properly: the vast territories of New Mexico and California. The Mexican government, for its part, continued not to recognize the independence of Texas, although Great Britain and France later did. Mexico itself was struggling as an independent nation and suffered from unstable government, with rule by dictators. It had failed to establish a republican form of government, although this had been its goal when it won independence from Spain in 1821. Few people lived in its northern provinces of California and New Mexico; California had only 15,000 Americans of European ancestry and 24,000 American Indians living on missions. (The total Indian population was much higher.) Many in the United States coveted these territories to complete national expansion. Yet despite its internal problems, Mexico was determined to keep all of its sovereignties intact.
Northern and southern states began to line up on different sides of the question of admitting Texas, due to the problem of slavery. Some proslavery southerners even hoped to divide the massive territory into several smaller slave states so as to increase the power of slaveholders in Congress. South Carolina, the most militantly proslavery and antiabolition state, went so far as to declare that if Texas was not admitted into the United States, then southern states should secede from the Union. There were not enough votes in the Senate, however, to get the needed two-thirds of the votes to ratify a treaty that would result in admitting Texas to the Union. But in the final days of his administration, President Tyler persuaded Congress to pass a joint resolution on the matter, which needed only a simple majority to pass. Tyler promptly extended the offer of statehood to Texas on his last day in office. Opponents of the measure argued that annexation would provoke a war with Mexico. Certainly the Mexican government was outraged; it had stated plainly in 1843 that it would regard any annexation of Texas as a declaration of war by the United States on Mexico. In response to the formal annexation in
1845 that occurred when Texas accepted the American offer of statehood, Mexico broke off diplomatic relations with the United States.
The new president, James K. Polk, had been nominated by the Democrats over Van Buren in 1844 in part because Polk had favored annexation, and the issue contributed to his victory in the general election over Whig candidate Henry Clay, who opposed it. Committed to expansionism, Polk was especially interested in acquiring California, which he offered to buy from Mexico. The southern nation refused, however, and also declined to negotiate with the United States about the boundary between the two nations. Mexico had maintained that the proper border was the Nueces River, which had been generally recognized as the boundary of Texas since the 18th century. Polk, pressing his expansionist agenda, contended that it was the river further south, the Rio Grande, which marked the true border between Mexico and the United States. To make the point that he was serious about the matter, in January
1846 he sent an army led by General Zachary Taylor to occupy the land in question between the Nueces and Rio Grande. The reason he gave to justify the action was that the soldiers were needed there to protect the new American state from a Mexican attack. However, Mexico saw this as a provocation and moved troops of its own into what it believed to be its territory by right.
Now face to face, soldiers of the two armies clashed and exchanged fire, with the Americans suffering 16 casualties in winning two encounters with the Mexicans, even though they were outmanned. Polk used the incident to ask Congress for a declaration of war against Mexico, charging that it had “invaded our territory and shed American blood on American soil.” Some in Congress, especially Whigs, remained skeptical of the whole business; first-term congressman Abraham Lincoln of Illinois famously asked Polk to specify where exactly U. S. sovereignty had been violated. There was other vocal opposition to war, especially in the Northeast; the Massachusetts legislature passed a
Engraving of the Battle of Buena Vista, February 23, 1847 (Library of Congress)
Resolution opposing it. Nevertheless, led by the Democrats, Congress went along with the president and declared war on Mexico on May 13, 1846. There was an especially great outcry of support for the decision in the South and West. It was from the states closest to Mexico, including Texas, that most of the military volunteers came—49,000 in all. Along the eastern seaboard, there was much less enthusiasm; the original 13 states contributed only about 13,000 volunteers.
In the conflict that followed, the United States won a series of military victories. Its initial strategy was to launch a two-pronged invasion of Mexico. Zachary Taylor’s goal was to invade central Mexico, and on the way he scored some victories in the northeastern part of the country, including capturing the crucial city of Monterrey. The American advance was slowed by severe problems with illness, as many U. S. soldiers fell sick and died from subtropical diseases to which they had no immunity. Taylor also halted progress until his army could receive further supplies, making the American army vulnerable to a Mexican attack. Fortunately for the Americans, though, the Mexican leadership was in chaos, as the government of President Mariano Paredes was overthrown and replaced by one led by the controversial former dictator, Antonio Lopez de Santa Anna. He had been in secret negotiations with the Americans and had promised that if he regained control of the Mexican government, he would seek to negotiate a peace treaty under which Mexico would cede territory to the United States.
Polk ordered the American navy and army to let Santa Anna, who had been living in exile in Cuba, pass through a naval blockade. The Mexican general landed and proceeded safely to Mexico City, where he proclaimed himself the new president of Mexico. Having done this, he quickly forgot the promise he had made to the United States and instead began to rally his nation to recommit to the war. He organized a large army of about 20,000 and led them north out of Mexico City toward the American position at Monterrey. Along the way he made the rash statement that he would defeat Taylor’s army, march all the way to Washington, and sign his peace treaty there. Many of Taylor’s men had been withdrawn from Monterrey and sent to Veracruz to take part in a seaborne landing led by General Wineield Scott. This left the remaining force under Taylor’s command at a 3-1 disadvantage to Santa Anna’s army as it took up defensive positions at Buena Vista. A fierce battle ensued with both sides suffering heavy casual-ties—especially the Mexicans, who were defeated despite their superior size. Among the American soldiers who distinguished themselves in this battle was Mississippi colonel Jefferson Davis, later president of the Confederate States of America.
Meanwhile, a second American force, led by Colonel Stephen Kearny, occupied New Mexico, including Santa Fe, and continued west into California, where it met with American naval forces to complete the conquest of that state. Kearny’s expedition was very successful, as he met with only token resistance from the inhabitants of those states, most of whom accepted the American victory.
Determined to capture Mexico City and bring the war to a successful conclusion, Polk ordered the opening of a third front. Winfield Scott led an army of volunteers, including some of Taylor’s men, in a coastal landing and proceeded to bombard the city of Veracruz; 1,500 Mexican civilians died in the attack. After inflicting heavy casualties on the Mexican army in street fighting, Scott’s forces marched on to Mexico City. The Mexican capital was well defended, and the U. S. Army, which included junior officers such as future Civil War generals Robert E. Lee, Ulysses S. Grant, and George McClellan, regrouped outside of the city to plan their assault. On the approach to Mexico City, the Americans met stiff resistance, but after heavy fighting they captured the Mexican capital in September 1847. Scott and his officers entered the presidential palace, over which the American flag was raised.
One of the Mexican units that inflicted the most punishment on the Americans was the San Patricio battalion, which consisted largely of Irish-American deserters from the U. S. Army. In all, more than 10 percent of American soldiers, many of whom were poor and some of whom were recent immigrants, had deserted from the allvolunteer army.
The American capture of Mexico City effectively ended the war. The relatively swift and decisive U. S. victory was due in large part to some important advantages in the areas of transportation and communications; the Americans had put telegraph, railroads and steamboats to good use in their military effort. In winning the war, the United States had suffered only about 1,700 combat-related deaths, although 11,000 more soldiers died of disease and related health problems.
In the postwar negotiations, the United States was represented by Nicholas Trist. Dealing from a position of strength, Trist persuaded the Mexican government to sign a treaty highly favorable to U. S. interests. Under the provisions of the Treaty of Guadalupe Hidalgo, signed in February 1848, the Rio Grande was established as the boundary between Mexico and Texas. Mexico also ceded New Mexico and most of California, recognized Texas as part of the United States, and received about $15 million in compensation. Some expansionist Democrats in the Senate demanded that all of Mexico be brought under the American flag, but Polk rebuffed that idea and was content with the astonishing gains agreed to in the treaty. In all, the United States gained 529,000 square miles from Mexico, including the part of California where the gold rush soon began, bringing people to that territory from around the nation and the world. The victory turned out to be a mixed blessing, however, as northerners and southerners began to disagree strenuously over whether the lands gained from Mexico would be slave or free. It took the Civil War to finally settle the question.
Further reading: Jack Bauer, The Mexican War: 18461848 (New York: Macmillan, 1974); John Eisenhower, So Far From God: The U. S. War With Mexico, 1846-1848 (New York: Random House, 1989); Robert Johannsen, To the Hall of the Montezumas: The Mexican War in the American Imagination (New York: Oxford University Press, 1985).
—Jason Duncan
World History
