By May 15, 1846, the U.S. Congress voted to go to war with Mexico, responding to escalating tensions and incidents along the Rio Grande, ultimately leading to the U.S.-Mexican War.
By May 15, the Congress voted to go to war with Mexico. This pivotal decision in 1846 marked a critical juncture in the U.S.-Mexican War, a conflict rooted in territorial disputes and tensions over the annexation of Texas. The annexation had heightened tensions between the two nations, with Mexico viewing it as a violation of its sovereignty.
The immediate precursor to the congressional vote was the Thornton Affair, where Mexican forces clashed with U.S. troops under Captain Seth Thornton along the Rio Grande. The incident further escalated hostilities, prompting President James K. Polk to present a war message to Congress on May 11, 1846, justifying military action against Mexico.
By May 13, the House of Representatives passed a resolution recognizing a state of war between the United States and Mexico. Two days later, on May 15, 1846, the Senate concurred with this resolution, officially declaring war. This marked the beginning of a conflict that would last for nearly two years, ending with the signing of the Treaty of Guadalupe Hidalgo in 1848.
In summary, by May 15, 1846, the U.S. Congress had voted to go to war with Mexico, formalizing a state of hostilities that had been building over issues related to territorial expansion and the annexation of Texas.