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- After a brief skirmish between the soldiers in April, President James Polk asked the U.S. Congress to declare war against Mexico. War fever swept the nation, but some Americans believed that the conflict was unnecessary and would have negative consequences for the United States.
Democrats, especially those in the Southwest, strongly favoured the Mexican-American War. Most Whigs, however, viewed the war as conscienceless land grabbing, and the Whig-controlled House voted 85 to 81 to censure Democratic Pres. James K. Polk for having “unnecessarily and unconstitutionally” initiated the war.
Oct 23, 2018 · The Mexican-American War and the massive territory gained reopened debates over slavery which diminished party alliances and increased sectional alliances. These debates over slavery eventually led to the demise of the Second Party System and paved the way for the rise of Republicanism.
- Overview
- “American blood on American soil”: Polk and the prelude to war
- Spot Resolutions and Civil Disobedience: American opposition to the war
The Mexican-American War was a conflict between the United States and Mexico, fought from April 1846 to February 1848. Won by the Americans and damned by its contemporary critics as expansionist, it resulted in the U.S. gaining more than 500,000 square miles (1,300,000 square km) of Mexican territory extending westward from the Rio Grande to the Pacific Ocean. It stemmed from the annexation of the Republic of Texas by the U.S. in 1845 and from a dispute over whether Texas ended at the Nueces River (the Mexican claim) or the Rio Grande (the U.S. claim).
What did the Mexican-American War have to do with Manifest Destiny?
The concept of Manifest Destiny held that the United States had the providential right to expand to the Pacific Ocean. In 1845 the U.S. annexed the Republic of Texas, which had won de facto independence from Mexico in the Texas Revolution (1835–36). When U.S. diplomatic efforts to establish agreement on the Texas-Mexico border and to purchase Mexico’s California and New Mexico territories failed, expansionist U.S. Pres. James K. Polk found a rationale to justify an attempt to take that land by force when U.S. and Mexican troops skirmished north of the Rio Grande on April 25, 1846.
Manifest Destiny
Read more about Manifest Destiny.
James K. Polk
Mexico severed relations with the United States in March 1845, shortly after the U.S. annexation of Texas. In September U.S. Pres. James K. Polk sent John Slidell on a secret mission to Mexico City to negotiate the disputed Texas border, settle U.S. claims against Mexico, and purchase New Mexico and California for up to $30 million. Mexican Pres. José Joaquín Herrera, aware in advance of Slidell’s intention of dismembering the country, refused to receive him. When Polk learned of the snub, he ordered troops under Gen. Zachary Taylor to occupy the disputed area between the Nueces and the Rio Grande (January 1846).
On May 9, 1846, Polk began to prepare a war message to Congress, justifying hostilities on the grounds of Mexican refusal to pay U.S. claims and refusal to negotiate with Slidell. That evening he received word that Mexican troops had crossed the Rio Grande on April 25 and attacked Taylor’s troops, killing or injuring 16 of them. In his quickly revised war message—delivered to Congress on May 11—Polk claimed that Mexico had “invaded our territory and shed American blood on American soil.”
Congress overwhelmingly approved a declaration of war on May 13, but the United States entered the war divided. Democrats, especially those in the Southwest, strongly favoured the conflict. Most Whigs viewed Polk’s motives as conscienceless land grabbing. Indeed, from the outset, Whigs in both the Senate and the House challenged the veracity of Polk’s assertion that the initial conflict between U.S. and Mexican forces had taken place in U.S. territory. Further, legislators were at odds over whether Polk had the right to unilaterally declare that a state of war existed. Principally at issue was where the encounter had actually taken place and the willingness of Americans to acknowledge the Mexican contention that the Nueces River formed the border between the two countries. Active Whig opposition not only to the legitimacy of Polk’s claim but also to the war itself continued well into the conflict. In December 1846 Polk accused his Whig doubters of treason. In January 1847 the by-then Whig-controlled House voted 85 to 81 to censure Polk for having “unnecessarily and unconstitutionally” initiated war with Mexico.
Britannica Quiz
A History of War
Among the most-aggressive challenges to the legitimacy of Polk’s casus belli was that offered by future president Abraham Lincoln, then a first-term member of the House of Representatives from Illinois. In December 1847 Lincoln introduced eight “Spot Resolutions,” which placed the analysis of Polk’s claim in a carefully delineated historical context that sought to
obtain a full knowledge of all the facts which go to establish whether the particular spot of soil on which the blood of our citizens was so shed was, or was not, our own soil at that time.
Ultimately, the House did not act on Lincoln’s resolutions, and Polk remained steadfast in his claim that the conflict was a just war.
- The Editors of Encyclopaedia Britannica
Nov 9, 2009 · The Mexican‑American War was a 1846‑1848 conflict over vast territories in the American West, which the Treaty of Guadalupe Hidalgo gave to the United States.
Ex-slave and prominent anti-slavery advocate Frederick Douglass opposed the Mexican–American War. In the United States, increasingly divided by sectional rivalry, the war was a partisan issue and an essential element in the origins of the American Civil War.
In September 1847, the U.S. army invaded the nation’s capital, Mexico City. Despite months of guerrilla warfare, Mexicans could not expel the occupying army. In February 1848, the two nations negotiated the Treaty of Guadalupe-Hidalgo to end the war.
Expansionistic fervor propelled the United States to war against Mexico in 1846. The United States had long argued that the Rio Grande was the border between Mexico and the United States, and at the end of the Texas war for independence Santa Anna had been pressured to agree.
