Mexican War Begins
The Mexican War, which officially began on May 13, 1846, stemmed from a complex backdrop of territorial disputes and the United States' ambition for westward expansion. The war was triggered by the controversial annexation of Texas in 1845, where differing views on the southern border—Rio Grande versus Nueces River—contributed to rising tensions between the two nations. President James K. Polk, advocating for territorial expansion, sought to negotiate the boundary and purchase California and New Mexico but was met with diplomatic refusal from Mexico.
Conflict escalated when Mexican forces clashed with American troops led by General Zachary Taylor near the disputed border, leading Polk to assert that American blood had been shed on American soil, thus fueling the push for war. The U.S. quickly gained military advantages, securing key victories and progressing into Mexican territory. The war saw significant battles and the U.S. establishment of a provisional government in California amid local rebellions.
Ultimately, the conflict concluded with the Treaty of Guadalupe Hidalgo in 1848, wherein Mexico recognized the Rio Grande as the official border and ceded large territories, including California and New Mexico, to the United States, marking a pivotal moment in the history of both nations.
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Mexican War Begins
Mexican War Begins
The congressional declaration of war against Mexico on May 12, 1846, was the culmination of a long series of events. Primarily, the powerful and expanding American nation was eager to acquire and settle Mexico's vast but thinly populated possessions in the Southwest, which included Texas. Further, Mexico was weak militarily, had practically no industrial base, and was not under the protection of any major European power, which made it an easy target for American expansion. Finally, President James K. Polk had promised to expand American territory as much as possible, a politically popular theme at the time, and war with Mexico was an ideal opportunity.
The 1845 annexation of Texas and controversy over what constituted its southern border was what set off the war more directly. Texas, according to Texans, extended all the way south to the Rio Grande. Mexico claimed, however, that Texas extended only as far as the Nueces River.
Even in the United States, the measure for annexation was controversial. Unable to secure the two-thirds vote necessary for Senate ratification of the measure, proponents presented it as a joint congressional resolution instead. Providing that Texas was to be admitted directly to statehood, the measure passed both chambers of Congress by a simple majority and was signed by President John Tyler on March 1, 1845, just before he left office and Polk came in. Texas became a state on December 29, 1845.
Accordingly, President Polk dispatched John Slidell on a diplomatic mission to Mexico in November 1845. Slidell's assignment was to secure Mexico's agreement on the Rio Grande as the southern boundary of Texas. If feasible, he also was to arrange the purchase of California and New Mexico, for which the United States was prepared to offer $30 million to $40 million and assumption of certain civilian legal claims against Mexico. Slidell's stay in Mexico dragged on for months while the Mexican government, under the pressure of local politics, declined to receive him. The final refusal came on March 12, 1846.
Four days earlier an American army under the command of General Zachary Taylor had begun advancing from the Nueces River, where he had been since the previous summer, to the mouth of the Rio Grande, where he arrived on March 24, 1846. Elements of Taylor's force followed the river inland to a point opposite Matamoros, where the Mexicans had assembled between 5,000 to 6,000 men. In the weeks that followed, both armies devoted themselves to building fortifications. The spark was not long in coming. On April 24 the Mexican commander sent word that, in his view, hostilities were already under way. That very day, 1,600 Mexicans crossed the Rio Grande, killed or wounded 16 members of an American reconnaissance party, and captured most of the rest. Advised of the news, President Polk delivered, with the approval of his cabinet, a war message in which he asserted that “Mexico has…shed American blood upon…American soil.” Although some Americans questioned whether hostilities had begun on American or on Mexican soil, a declaration of war was passed by the House of Representatives the same day, May 11, and by the Senate the following day. Thus, the war with Mexico officially began on May 13, 1846.
Even before war had been declared officially, “Old Rough and Ready” Taylor, who became a national hero during the hostilities, had driven the Mexicans back across the Rio Grande. Taylor won victories at Palo Alto and Resaca de la Palma, in the vicinity of Matamoros. He occupied Matamoros itself on May 18 and took Monterey on September 24. The conflict in northern Mexico ended before the winter was over with Taylor's defeat of the victor of the Alamo, General Antonio López de Santa Anna, in the battle of Buena Vista on February 22 and 23, 1847.
In the meantime, two other aspects of the war went forward. These were the United States' blockade of Mexico's east and west coast ports and the occupation of New Mexico, a vast region embracing most of what is now the American southwest, by Colonel Stephen Kearny. From New Mexico, Kearny's instructions took him with part of his force to California. On the way he learned of the “bear flag revolt” of a handful of American settlers in the Sacramento Valley. The settlers had declared California independent in June 1845 and prepared to challenge Mexico as the Texas settlers had done earlier. The adventurer Kit Carson and Captain John C. Frémont of the U.S. Army, who was in California at the time, joined forces with the rebels. On the California coast, the navy took possession of Monterey, San Francisco, and Los Angeles. In the north of California other points were occupied with little resistance. When Kearny arrived in San Diego in December 1846, he was able to proceed with setting up a provisional California government.
Back on the Mexican front, General Winfield Scott meanwhile proposed, and Polk approved, an expedition to Veracruz. When that city fell to Scott on March 29, 1847, the way was opened to victories at Cerro Gordo, Contreras, Churubusco, Molino del Rey, and the hill of Chapultepec, which dominated the capital, Mexico City. When Chapultepec was won, the American forces entered Mexico City on September 13 and 14, 1847. For all intents and purposes, the war ended several days later. Technically, however, it was concluded on February 2, 1848, with the signing of the Treaty of Guadalupe Hidalgo. In accordance with the terms of this agreement, Mexico gave up all claim to Texas and recognized the Rio Grande as its own northern boundary. Mexico also ceded both California and New Mexico to the United States. In return the United States paid Mexico $15 million and assumed the claims of its nationals against the Mexican government.