Watch Full Movie Online. One of the most controversial conflicts in U.S. history, the Mexican-American War erupted as President James K. Polk sought to extend the borders of the nation to the Pacific, taking by force whatever territory stood in the way. This special, produced by The History Channel and hosted by Oscar de la Hoya, looks at the war from the perspective of both countries, and chronicles the fighting from its inception to its conclusion with the Treaty of Guadalupe Hidalgo.