The Mexican-American War was a war fought between the United States and Mexico between 1846 and 1848. It is also called the US-Mexico War. In the US it is also known as the Mexican War; in Mexico it is also known as the North American Invasion of Mexico, the United States War Against Mexico, and the War of Northern Aggression (this last name is more commonly used in the Southern United States to refer to the American Civil War).
The war grew out of unresolved conflicts between Mexico and Texas. After having won its independence from Mexico in 1836, the Republic of Texas was annexed by the United States in 1845; however, the southern and western borders of Texas remained disputed during the Republic's lifetime. That same year tensions between the two countries over territory were raised when the United States government offered to pay off the Mexican debt to American settlers if Mexico allowed the US to purchase the territories of Alta California and Nuevo México from Mexico, which some Mexicans found offensive.
The declaration of war
President James K. Polk ordered General Zachary Taylor to seize disputed Texan land settled by Mexicans. Fighting began on April 24, 1846 when Mexican cavalry entered an area claimed by both the US and Mexico, between the Rio Grande and Nueces River, and surrounded a US scouting party under General Zachary Taylor; several were killed. After the border clash and battles at Palo Alto and Resaca de la Palma, the U.S. Congress declared war on May 13, 1846. Northern Whigs generally opposed the declaration of war while Southerners supported it. Mexico declared war on May 23.
After the declaration of war, US forces invaded Mexico on several fronts. In the Pacific, the US Navy sent John D. Sloat to occupy California and claim it for the US because of concerns that Britain might also attempt to occupy the area. He linked up with US colonists in Northern California who had previously declared an independent California Republic and occupied some key cities. Meanwhile, US army troops under Stephen W. Kearny occupied Santa Fe, New Mexico, and Kearny led a small force to California where, after some initial reverses, he united with naval reinforcements under Robert F. Stockton to occupy San Diego and Los Angeles.
The main force led by Taylor continued across the Rio Grande into Mexico, winning the Battle of Monterrey in September of 1846. Mexican President Antonio López de Santa Anna personally marched north to fight Taylor but was defeated at the battle of Buena Vista on February 22, 1847. Meanwhile, rather than reinforce Taylor's army for a continued advance, President Polk sent a second army under US general Winfield Scott in March, which was transported to the port of Veracruz by sea to begin an invasion of the Mexican heartland. Scott won the Battle of Vera Cruz and marched toward Mexico City, winning the battles of Cerro Gordo and Chapultepec and occupying the Mexican capital.
The Treaty of Cahuenga, signed on January 13, 1847, ended the fighting in California. The Treaty of Guadalupe Hidalgo, signed on February 2, 1848, ended the War and gave the US undisputed control of Texas as well as California and most of Arizona and New Mexico.
An interesting side note of the war was the Saint Patrick's Battalion (San Patricios), a group, approximately 500-strong, of (largely Irish-born) Americans who deserted the US Army in favor of the Mexican side. Many of them fought against what they alleged was brutal, racist discrimination received from the US. Many identified with Mexico as Catholics. They were hanged by the US; making sure that the last thing these Irish men saw was the lowering of the Mexican flag and the raising of the US flag as the war was won. Some historians claim that these men were prisoners of war. Others argue that they were traitors and deserters. There are many monuments to these soldiers in present-day Mexico.
According to data from the United States Department of Veterans Affairs, the last surviving US veteran of the conflict, Owen Thomas Edgar, died on September 3, 1929 at the age of 98.
The war is often considered an example of the US government's then-ongoing expansionist policies in North America, as defined by the doctrine of Manifest Destiny.
Political implications of the war
Mexico lost much of its territory in the war, leaving it with a lasting bitterness towards the US. Santa Anna fled to exile in Venezuela.
In the US, the war was widely supported in the southern states but opposed in the northern states. This division largely developed from expectations of how American expansion would affect the issue of slavery. At the time, Texas recognized the institution of slavery, but Mexico did not. Many Northern abolitionists viewed the war as an attempt by the slave-owners to expand slavery and assure their continued influence in the federal government. Henry David Thoreau wrote his essay Civil Disobedience and refused to pay taxes because of this war.
The main issue which furthered sectionalism was the expansion of slavery into the national territories. The Missouri Compromise banned slavery in national territories north of 36 degrees, 30 minutes (roughly the southern border of Missouri). Also, the Senate was constructed to give equal balance to slave and free states. The Missouri Compromise, however, left room for more free states then slave states, and if continued would upset the balance of power within the Senate. Thus, many southerners supported the war to provide more room for slavery to expand (believing that if slavery were contained, then it would die out).
During the first year of the war, Congressman David Wilmot (D-PA) introduced a bill which would prohibit slavery in any new territory captured from Mexico. This bill, which became known as the Wilmot Proviso caused an immediate outcry from southerners on both sides of the congressional aisle. To southerners it looked as if the north was willing to abandon parity within the senate, and the Wilmot Proviso sparked further hostility between the sections. The bill itself was passed by the House of Representatives but failed in the Senate, with both votes on sectional lines.
In 1848 the Democrats proposed a new solution, known as Popular Sovereignty. This would allow for voters within a territory to determine for themselves whether or not they would allow slavery within their territory. However, the election of Zachary Taylor, a southern Whig, as President indicated that the doctrine would not be national policy. Taylor supported Wilmot, and thus helped spark a political crisis in his administration, resulting in the Compromise of 1850.
Ulysses S. Grant declared the Mexican-American war to be "one of the most unjust ever waged by a stronger against a weaker nation" and one of the causes of the American Civil War: "The occupation, separation and annexation [of Texas] were ... a conspiracy to acquire territory out of which slave states might be formed for the American Union." Many of the generals of the latter war had fought in the former, including Grant and Robert E. Lee. General Porfirio Díaz, president of Mexico from 1877–1911) would later lament: "¡Pobre México! Tan lejos de Dios, y tan cerca de los Estados Unidos." ("Poor Mexico! So far from God, and so close to the United States.")
- Battles of the Mexican-American War
- PBS site of US-Mexican war program (http://www.pbs.org/kera/usmexicanwar)
- Personal Memoirs of Ulysses S. Grant (http://www.gutenberg.net/etext/4367) from Project Gutenberg