The Annexation of Texas
In January 1844, Texas and the United States signed a annexation treaty that would allow Texas to become a state of the U.S. This treaty, however, was rejected by the senate on the basis that Texas was a slave state. However, in the election of that year, the citizens of the United States clearly showed their wishes to have Texas as a state and sole control of Oregon territory.
Almost a year and 1/2 later on March 1, 1845, Congress passed a joint resolution to annex of Texas, however, this treaty left the United States with less advantage than the one in 1844. Three days before he retired from office, President Tyler signed the annexation and on December 29, 1845, Texas was formally admitted as the twenty-eighth state, one of fifteen having slavery.
Mexico, however, never respected Texas' independence and felt the annexation an insult to their nation. Many citizens felt the need to go to war with the United States. However, due to internal conflicts, this was not a very good idea. But it was not helped by the army coup in December 1846 of General Jose Joaquin de Herrera. He was replaced by Mariano Padres.
War
In November 1846, President
James Polk sent
John Slidell to meet with President Herrera with the intent of attempting to buy the land that was ceded to the United States following the
Treaty of Guadalupe Hidalgo. He returned in March of the following year...without ever meeting either presidents.
During Slidell's stay in Mexico, things between the 2 nations had become rather tense, to say the least. Still bitter over the the annexation of Texas, arguments developed over the boundary of Texas with te U.S. and Mexico so President Polk sent General Zachary Taylor to the Rio Grande.
On April 25, 1846 Mexican troops attacked the U.S troops stationed there in a small but history altering skirmish. And shortly there after on May 13, Congress declared war on Mexico.
Despite the larger size of the Mexican army, it was woefully backwards in many respects compared to the United States which would cost them dearly by the end of the war 2 years later. The American strategy was a 3 pronged attack the intent of seizing control of northern Mexico to force an early peace.
Two American armies moved south from Texas, while a third force under Colonel Kearny travelled west to Santa Fe, New Mexico and then to California. In a series of battles at Palo Alto and Resaca de Palma, the army of General Zachary Taylor defeated the Mexican forces and began to move south after inflicting severe casualtes on the Mexicans.
Interestingly, soon after the declaration of war white pionners in California began a revolt and formed the Bear Flag Republic with its capital in Sonoma. It last scarcely a month before the arrival of the American Commodore John Sloat who took Monterey without a fight (The city barely had any powder) while Colonel Stephen K. Kearney marched towards the soon-to-be state and scarcely 1/2 a month since Congress declared war, Alta California governor Pío Píco capitulated to the Americans on January 13, 1847 (For more info on the battles in the Los Angeles area, see Battles for Los Angeles).
Meanwhile, by September, the forces of Zachery Taylor attacked the city of Monterrey in a bloody three-day battle with Mexican troops under the command of General Ampudia. Following the capture of the city by the Americans, a temporary truce was reached to allow both sides to rest.
However, during the short truce, former Mexican president, Santa Anna had returned from exile, and raised a 20,000 man strong army to take on the Americans. As the war dragged on, with the Mexicans losing land and the major battles, they still refused to sue for peace. President Polk soon realized that only a complete victory over the Mexicans would end the war.
To achive this goal, General Winfield Scott proposed what would become the largest amphibious landing in history, (at that time), to seize Mexico City. Executed on March 9, 1847 with the landing of 12,000 men under Scott's command at the port city of Veracruz. The expedition took 6 months and several bloody battles including the Battle of Cerro Gordo (April 18), Contreras (August 20), Churubusco (August 20), Molino del Rey (September 8) and Chapultepec (September 13), before the Americans finally enter the capital on September 14.
From then until the signing of the Treaty of Guadalupe Hidalgo on February 2, 1848. Santa Anna continued to harrass the Americans in a futile attempt to save Mexico from surrendering. It finally ended by his government asking for his military resignation (He had resigned the presidency earlier).
Causes of the War
The Mexican-American War was the first war that
United States fought that resulted from the idea of a
Manifest Destiny. It was part of the massive era of
expansionism sparked by
Andrew Jackson. It did however, complete the Manifest Destiny's idea of a nation from "sea to shining sea" at least. This is not to say that Mexico wasn't exactly against going to war, they were very bitter of the independence of Texas, and even more so by the United States' annexation of it. Both wanted war to some extent, and they got it.
Sources
http://www.historyguy.com/Mexican-American_War.html
http://www.ccnet.com/~laplaza/calhist4.htm
http://www.pbs.org/kera/usmexicanwar/