Texass struggle for independence from Mexico and its annexation by the United States led to the Mexican War. From 1846 to 1848, the United States fought Mexico to acquire land stretching from Texas to the Pacific Ocean.
By the 1830s, American settlers in Mexicos Texas territory outnumbered native Mexicans. Americans felt oppressed by Mexican rule and, under the leadership of Stephen Austin and Sam Houston, declared independence in 1835. A Mexican army under General Antonio Santa Anna attacked and slaughtered Texas rebels at the Alamo, but Houston rallied support and crushed Santa Anna at San Jacinto.
Struggling as an independent country, the Republic of Texas sought to become part of the United States. Although many in Congress opposed the move, the United States annexed Texas in 1845.
Manifest Destiny in Action
President James K. Polk came into office in 1845 determined to acquire additional territory from Mexico.
Polk believed that obtaining the sparsely populated Mexican land that stretched from Texas to California was critical to the future of the United States. The president hoped to purchase, not conquer, the land, but Mexico rebuffed his advances. Polk ordered American troops under Zachary Taylor to march to the Rio Grande River. Violence erupted, and Polk, claiming that Mexico fired first, asked Congress to declare war. Many Americans, including Illinois congressman Abraham Lincoln, opposed the war and questioned whether the fight began on American soil. But Polk prevailed stating, The grievous wrongs perpetrated by Mexico upon our citizens throughout a long period of years remain unredressed . . . the two nations are now at war.
Fighting over the war was carried out in newspapers. Journalist John L. OSullivan, spread the idea of manifest destiny writing, [It is] the right of our manifest destiny to over spread and to possess the whole of the continent which Providence has given us for the development of the great experiment of liberty. But Horace Greeley editor of the New York Tribune, was opposed to the war. He wrote, People of the United States! Your Rulers are precipitating you into a fathomless abyss of crime and calamity! Why sleep you thoughtless on its verge, as though this was not your business . . . ? Awake and arrest the work of butchery ere it shall be too late to preserve your souls from the guilt of wholesale slaughter!
Beginning the War
To fight Mexico, the United States had to mobilize, equip, and transport a large force, including both army and navy components.
President Polk planned a complex campaign. He sent one army under Stephen Kearny to capture New Mexico and then march on to California. Commodore John D. Sloat assaulted California from the sea. Zachary Taylor attacked the main Mexican force from the north with a second army. Battles were hard and marches long.
All three thrusts succeeded. Taylor won at Palo Alto and Saltillo. Kearny quickly captured Santa Fe, while the navy and army succeeded in California. Junior officers were of great importancemany had trained at the Military Academy at West Point. At the Battle of Cerro Gordo in 1847, General Winfield Scott demonstrated his effective leadership. Instead of assaulting a larger Mexican force head-on, Scott had his engineers carefully survey and map the area. They helped him find high ground overlooking the enemy. He moved artillery to that position and attacked from two directions, winning the battle.
Defeating the Mexican Army
Despite its losses in New Mexico and California, and on its northern front, Mexico refused to surrender. To finish the war, President Polk followed the advice of his general in chief, Winfield Scott, and sent an army to capture Mexico City. He chose Scott himself to make an amphibious landing at Veracruz and then follow the path Hernando Cortés took centuries earlier when he defeated the Aztecs. Scott planned and executed a brilliant campaign, in which he consistently defeated larger forces through superior tactics and bold maneuvers. The Treaty of Guadalupe Hidalgo in 1848 ended the war.
On February 2, 1848, the treaty was signed in Guadalupe Hidalgo. It called for Mexico to cede 55 percent of its territory, including what is now Arizona, California, New Mexico, and Texas, and parts of Colorado, Nevada and Utah, in exchange for fifteen million dollars in war compensation. After the Treaty of Guadalupe Hidalgo, Mexicans living in the new United States territory had to adapt to becoming Americans. Many Mexicans who lived in the territory lost to the United States decided to stay and become American citizens. Integration proved difficult. The U.S. government refused to accept land claims based on tradition or limited documentation, and many Mexicans lost their holdings.
With the discovery of gold in California and the ensuing gold rush, white settlement accelerated. Many of the attitudes of the new arrivals conflicted with Mexican culture and its strong Catholic faith. Still, earlier traditions survived and made the resulting society of the West distinctly different from that of the eastern states.