how did the u.s. first attempt to acquire mexico’s northern territories
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.