Mexican-American War
The Mexican-American War (1846-1848) was a conflict between the United States and Mexico, sparked by the US annexation of Texas in 1845. Hoping to seize even more territory from Mexico, US President James K. Polk (served 1845-1849) used the Texas dispute to provoke a war, precipitating the US invasions of California, New Mexico, and the Mexican heartland. After the fall of Mexico City in September 1847, the Mexican government relinquished 529,000 square miles of territory to the US in the Treaty of Guadalupe Hidalgo. The war has often been regarded as an unjust invasion, both by contemporaries and later historians, and would only inflame the sectional divisions in the US that would lead to the American Civil War (1861-1865).
Background
In 1821, after over a decade of perpetual conflict, the Mexican War of Independence came to an end. For Mexico, the cost of winning independence from Spain came not only in blood but also in coin, as the once prosperous colony found its economy in tatters. Money barely circulated, the silver mines of Zacatecas and Guanajuato had been devastated, and throughout the country, ranches and farms stood deserted. To revitalize its economy and protect its vulnerable northern territories from Comanche and Apache raids, Mexico decided to invite Anglo-American settlers into Texas to exploit the region's untapped resources. Thousands of Anglo-Americans flooded into Texas – many of them bringing slaves – so that by 1830, the US transplants outnumbered the Hispanic Tejanos by more than two to one. Eventually, relations between these Anglo-American settlers and the Mexican government deteriorated, especially after Mexico abolished slavery. In October 1835, the settlers – who called themselves 'Texians' – rebelled, sparking the Texas Revolution (1835-36).
Initially, the Mexican army under Antonio López de Santa Anna (1794-1876) got the better of the rebels, scoring a victory at the Battle of the Alamo (23 February to 6 March 1836) and butchering 400 Texian prisoners at the Goliad Massacre (27 March). But the tide abruptly turned at the Battle of San Jacinto (21 April), when Texian forces under Gen. Sam Houston (1793-1863) surprised and defeated the Mexican army. Santa Anna was taken captive and forced to sign a treaty recognizing Texas' independence. But since the treaty was signed under duress – Santa Anna likely would have been executed had he not signed – it was not ratified by the Mexican Congress, which refused to recognize Texian independence. Thus, for the next several years, periodic fighting erupted across the Mexico-Texas border, as Texas began to operate like an independent republic. These events were closely watched by the United States. Since 1803, the US had claimed Texas, believing it to have been a rightful part of the Louisiana Purchase. Spain, however, had denied this claim and resisted every US attempt to buy the territory. Now, the US saw its opportunity, and, in 1843, President John Tyler (served 1841-1845) quietly opened talks to annex Texas.
While some Texians preferred to remain independent, others saw the benefit of joining the United States. The idea also gained momentum in the US where Southern Democrats, who wished to expand the institution of slavery, relished the idea of adding another 'slave state' to the Union, while other Americans believed Texas' annexation would be a huge step toward the 'Manifest Destiny' of their nation to spread its influence across the continent. After some hiccups, the US Congress passed a resolution offering annexation to Texas in February 1845 – Texas accepted and, in December, became the 28th state. This, of course, was seen as a hostile act by Mexico, who had yet to recognize Texas' independence, let alone its annexation to the US. Nor did Mexico agree with Texas' assertion that the Rio Grande constituted its southern boundary; historically, the border of Mexican Texas had ended at the Nueces River, 150 miles (240 km) north of the line Texas now claimed. But the newly elected US president, James K. Polk (1795-1849), did not care what Mexico thought – "I regard the question of annexation as belonging exclusively to the United States and Texas," he proclaimed in his inaugural address (quoted in Howe, 733).
A Democrat in the mold of Andrew Jackson (1767-1845), Polk had run on a platform of expansionism. Promising to guide the US to its 'Manifest Destiny' on the coasts of the Pacific, he was interested not only in acquiring Texas but also New Mexico and California. In November 1845, he dispatched a secret representative, John Slidell, to Mexico City with an offer to buy the Rio Grande border, New Mexico, and Alta California, all for $25 million. Once Slidell's purpose became known, however, his very presence in Mexico City was perceived as an insult. Negotiations were further hampered by the instability of the Mexican government; in 1846 alone, the Mexican presidency exchanged hands four times. Frustrated that he was getting nowhere with the negotiations, Slidell reported back to Washington that "a war will probably be the best mode of settling our affairs with Mexico" (quoted in Howe, 737). But Polk was way ahead of him – having anticipated that the negotiations would fail, he had spent the last few months positioning his armies to provoke a war with Mexico and seize the lands he desired by force.
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⇒ Mexican-American War
