Road to War: U.S.–Mexico Conflict (1846)

Key Events Leading to the Mexican–American War

1. Texas Annexation (1845) – U.S. absorbs Republic of Texas; Mexico never recognized its independence.
2. Border Dispute – Mexico claimed Nueces River; U.S. insisted on Rio Grande.
3. Manifest Destiny & California – Polk administration coveted California, New Mexico.
4. Slidell Mission Fails (1845) – Mexico refuses to receive U.S. envoy offering purchase/recognition.
5. Taylor Marches to Rio Grande (1846) – U.S. troops occupy disputed territory; Mexico views as invasion.
6. Thornton Affair (Apr 25, 1846) – Mexican cavalry ambushes U.S. patrol; 11 killed.
7. U.S. Declares War (May 13, 1846) – Polk: "Mexico has shed American blood on American soil."
8. Invasion of Mexico – U.S. forces seize California, New Mexico, advance on Mexico City.

Territorial ambition, diplomatic failure, and a contested border ignited the conflict.