“Mr. Polk’s War”
Polk was moved to action. He offered Mexico $40 million for the California territory. The Mexican president not only turned down the offer, but he refused even to see President Polk’s emissary. Thus rudely rebuffed, Polk commissioned the U.S. consul at Monterey (California), Thomas O. Larkin, to organize California’s small but powerful American community into a separatist movement sympathetic to annexation by the U.S. In the meantime, John Charles Fremont, an intrepid western explorer surveying potential transcontinental railroad routes for the U.S. Bureau of Topographical Engineers, marched onto the stage with the so-called Bear Flag Rebellion. California’s independence from Mexico was proclaimed.
As far as Mexico was concerned, the independence of California merely added insult to injury. Mexico disputed with the United States the boundary of the new state of Texas. President Polk dispatched troops to Texas and, on May 13, 1846, declared war on Mexico. But even before the official declaration, Mexican forces laid siege against Fort Texas—present-day Brownsville—on May 1.
General Zachary Taylor, marching to the relief of the fort, faced 6,000 Mexican troops with a mere 2,000 Americans, but he nevertheless emerged victorious in the May 8 Battle of Palo Alto. The battle set the pattern for the rest of the conflict. Usually outnumbered, the Americans almost always outmatched the poorly led Mexican forces.
In the meantime, early in June, official U.S. action commenced against the Mexicans in California as Stephen Watts Kearny led the “Army of the West” from Fort Leavenworth, Kansas, to California via New Mexico. Near Santa Fe, at steep-walled Apache Canyon, New Mexico’s Governor Manuel Armijo set up an ambush to destroy Kearny’s column, but the governor’s ill-disciplined and ill-equipped troops panicked and dispersed. Kearny passed through the canyon unopposed, Santa Fe was taken, and on August 15, New Mexico was annexed to the United States, all without firing a shot.
General Taylor attacked Monterrey (Mexico) on September 20, 1846, taking the city after a four-day siege. Taylor declined to capitalize on what he had gained and allowed Mexican forces to withdraw. In the meantime, the remarkably resilient Antonio Lopez de Santa Anna, who had been living as an exile in Cuba after a rebellion had ended his dictatorship of Mexico, made a proposal to the government of the United States. He pledged to help the U.S. win the war, to secure a Rio Grande boundary for Texas, and to secure a California boundary through San Francisco Bay. In return, Santa Anna asked for $30 million and safe passage to Mexico. American officials were prudent enough not to pay him, but Santa Anna was allowed to return to his homeland—whereupon he began assembling an army to defeat Zachary Taylor.
By January 1847, Santa Anna had gathered 18,000 men, about 15,000 of whom he hurled against Taylor’s 4,800-man force at Buena Vista. After two days of bloody battle, Taylor—incredibly—forced Santa Anna’s withdrawal on February 23. Despite this signal victory, President Polk was distressed by Taylor’s repeated reluctance to capitalize on his victories and also worried lest he make a military celebrity out of a potential political rival. So Polk replaced Taylor with General Winfield Scott, hero of the War of 1812. On March 9, Scott launched an invasion of Veracruz, beginning with the first amphibious assault in U.S. military history. He laid siege against the fortress at Veracruz for 18 days, forcing Santa Anna to withdraw to the steep Cerro Gordo canyon with 8,000 of his best troops.
Scott declined the frontal attack the Mexicans expected. Instead, he sent part of his force to cut paths up either side of Cerro Gordo and attacked in a pincers movement, sending Santa Anna’s troops into headlong retreat all the way to Mexico City. Scott took the kind of gamble Taylor would not have taken and boldly severed his rapidly pursuing army from its slower-moving supply lines. On September 13, Chapultepec Palace, the seemingly impregnable fortress guarding Mexico City, fell to Scott. (The Palace had been defended by a force that included teenage cadets from the Mexican Military College. These cadets are celebrated in Mexican history as “Los Ninos,” the children.) On September 17, Santa Anna surrendered.
The Mexican War ended with the Treaty of Guadalupe Hidalgo, which was ratified by the Senate on March 10, 1848. Mexico ceded to the United States New Mexico (which also included parts of the present states of Utah, Nevada, Arizona, and Colorado) and California. The Mexicans also renounced claims to Texas above the Rio Grande.