The United States declared war on Mexico on April 25th, 1846 and hostilities would continue until February 2nd, 1848. The United States has been involved in many different wars, but Ernesto Chavez’s book The U.S War with Mexico illuminates why this one took place and what happened. The book clearly outlines the reasons. The war against Mexico was a very complicated war, despite its short life. The intricacies that brought this feud to a head are numerous and vary from concepts. Racial discrimination, Manifest Destiny, Expansionist Policies, Slavery, and government all were aspects that had a role in the U.S war with Mexico. Americans felt superior to other nations and races which made it hard for those who were not white with European Lineage. The Unites States had adopted a belief system that not only left them feeling more noble and civilized, but one that gave them the right to expand anywhere Americans wanted; moreover, the government worked to gain advantages for the country. Slavery had a very interesting role as those who were for and against it had their own agenda in attempting to control what happened to the war on Mexico.