The Mexican American War took place from 1846-48. President Polk ordered an invasion of the disputed territory between Texas and Mexico, causing mexicans to fire on american troops and thus a war. Due to lacking resources, Mexico had a hard time fighting the war against americans whom were firmly believing in Manifest Destiny at that point. In the end, Mexico lost 1/3 of their territory to the US in the Treaty of Guadalupe Hidalgo. http://www.history.com/topics/mexican-american-war ----Video Link----https://www.youtube.com/watch?v=bNgotEobNOw ----Video---- The video reviews the causes and results of the Mexican American War and what occurs during the war such as the boarder dispute and US troops pressing past the disputed territory and into Mexico itself.