The Mexican-American War (also referred to as the American-Mexican War) was a conflict between the United States of America and Mexico from 1846 to 1848. It was largely a result of the Texas War of Independence in 1836, and the United States' subsequent annexation of Texas in 1845. The war was driven also by the idea of a "Manifest Destiny" that Americans believed was a God-given right to control the North American continent. While tensions grew for several years, war was finally declared after a skirmish broke out in a disputed region of southern Texas, between the Rio Grande and Nueces Rivers.
Buildup to War
One of the driving forces for the war was the popular notion of Manifest Destiny. This belief held that it was the American peoples' birthright to control the whole of the American continent. This obviously gave rise to conflicts with many nations over territorial claims. The secret Ostend Manifesto, written in Ostend, Belgium in 1854 by U.S. ambassadors, concerning the annexation of Cuba was perhaps the first warning of the conflicts Manifest Destiny would soon cause. Northern presses feared it would be used to spread slavery, and their outcries prevented the Manifesto's plans from ever being put into effect. While this did not lead to armed conflict, it was only a matter of time before Manifest Destiny would be put to the test. Expansionist James K. Polk was sworn into office in January of 1845. "Fifty-Four Forty or Fight!" became a catchphrase for the annexation of the entire Oregon Country, then co-owned with Great Britain. The slogan referred to the region's northern boundary of 54°40ʹ N latitude. The border eventually was agreed upon at the 49th Parallel. Manifest Destiny's desire to expand into the Mexican-controlled lands of California would eventually lead to war.
Texas War of Independence
Manifest Destiny would come to a boil during the Texas War of Independence in 1835, in which the region of Texas fought Mexico for its independence. Soon after the war, Texas petitioned the United States for statehood. Southern Democrats wished to see the state added as a slave state, while the Northern Republicans opposed expansion into Texas. With the election of Polk, Texas was brought into the Union. A no-man's land between the Rio Grande and Nueces River was disputed between the United States and Mexico. Mexico contended that it did not grant that region independence, while the U.S. claimed it was annexed along with Texas. The borders of the region were fortified with troops from both nations. On April 25, 1846, President Polk ordered Captain Seth Thornton to cross the Nueces into the disputed lands. Thornton was attacked by Mexican troops, and was forced to surrender, after the loss of sixteen American soldiers. Polk's plan had worked, and he now had a legitimate reason for war with Mexico, and would soon be able to lay claim to the lands he would acquire. In an address to Congress, he famously declared that "American blood has been shed on American soil," affirming the American belief that the Rio Grande was the southern border of Texas. War was officially declared by the United States on May 13, and Mexico followed suit on July 7.
Overview of War
The U.S. invaded northern Mexico from two directions, in an attempt to quickly sieze lands and force an early surrender. Colonel Stephen Kearny commanded the forces that headed west from Kansas to Santa Fe (and later to California to reinforce Captain John C. Frémont, who was stationed there before the war). The second front was opened by General Zachary Taylor, who moved southward after repetitive victories against the defending Ejército del Norte (Army of the North).
Colonel John C. Frémont was near Monterey, California, on his way to Oregon, when news of the war reached California. On June 15, in nearby Sonoma, a group of American settlers seized a Mexican garrison and proclaimed an independent California Republic. Frémont's forces took over the area a week later. The U.S. Navy, under command of Commodore Robert F. Stockton, soon arrived and put Frémont's forces undeer their command. The combined forces had occupied San Francisco, Monterey, Sonoma, Sacramento, and Los Angeles by August. These troops held out against Californios (ethnic Mexicans living in California) until January of 1847, when the Treaty of Cahuenga was signed.
Taylor's army won two quick victories in Palo Alto and Resaca de la Palma in May of 1846, allowing him to enter Northern Mexico. In September, he captured the large city of Monterey after a three-day battle. After the battle, a temporary truce was enacted, during which the Mexican government refused to make peace. The turmoil in Mexico allowed former President Antonio López de Santa Anna to gain re-election. A fresh army of 20,000 men was trained by the new President. At the Battle of Buena Vista, General Taylor opened up the route into the heart of Mexico that would allow the future capture of the capital. On March 9, 1847, in the largest amphibious landing in history up to that time, General Winfield Scott brought 12,000 men ashore at Veracruz, Mexico. Polk gave Scott command of this force, largely in an attempt to quiet the public's love of Taylor. Polk, a Democrat, feared that Taylor, a Whig, would use his popularity as a war hero to unseat him in the next election. Scott met Santa Anna in several engagements through September, eventually reaching Mexico City. The last building to hold out against Scott was a military academy at Chapultepec Castle. Four teenaged cadets (the youngest of whom was thirteen years old) and their 20-year-old lieutenant squadron leader fought to the death to defend their city. El Día de Los Niños Heroes de Chapultepec (Day of the Boy Heroes of Chapultepec) is celebrated every September 13, the anniversary of the battle, and honors the bravery of the boys. With the fall of Mexico City, the Mexican Army surrendered.
Consequences of the War
General Taylor, nicknamed "Old Rough and Ready" used his popularity to win the Presidency in 1848, despite Polk's efforts to prevent such an election. Other generals would also run for President, including the Republican Party's first candidate, John C. Frémont. The war also provided experience for the men who would be leaders during the soon-to-come American Civil War, including Ambrose Burnside, Robert E. Lee, Winfield Scott, James Longstreet, Ulysses S. Grant, "Stonewall" Jackson, George McClellan, Jefferson Davis, and George Meade
United States: 13,780 dead.Mexico: approximately 25,000.
- Bauer, K. Jack "The Mexican-American War 1846-48"