who led a small force to overthrow mexican rule in northern california
California Republic In June 1846, thirty-three American immigrants in Alta California rebelled against the Mexican department's[notes 1][2] government. The immigrants had not been allowed to buy or rent land and had been threatened with expulsion from California because they had entered illegally without official permission.[3][4] Mexican officials were concerned about a coming war with the United States coupled with the growing influx of Americans into California. The rebellion was soon overtaken by the beginning of the Mexican–American War.
Mexican–American War In 1845, newly elected U.S. President James K. Polk made a proposition to the Mexican government to purchase the disputed lands between the Nueces River and the Rio Grande river further south. When that offer was rejected, President Polk moved U.S. troops commanded by Major General Zachary Taylor further south into the disputed territory. Mexican forces attacked an American Army outpost ("Thornton Affair") in the occupied territory, killing 12 U.S. soldiers and capturing 52. These same Mexican troops later laid siege to an American fort along the Rio Grande.[6] Polk cited this attack as an invasion of U.S. territory and requested that the Congress declare war.