The Mexican War happened in 1846. Ten years earlier Davy Crockett and Jim Bowie had fought for Texan independence. Supporters of slavery in the US wanted an excuse to expand the number of slave states in order to out-vote any antislavery laws, while capitalists wanted to gain access to the Pacific and open up trade with Asia.. A patrol of US troops strayed onto the wrong side of the border and were attacked by the Mexicans. This was the excuse the imperialists wanted. Despite being outnumbered by the better equipped US the Mexicans held out for 2 years but eventually Mexico City fell and California was seized as a prize. America was punished for this act of aggression in 1861 when civil war broke out
