In the presidential election of 1844, James Polk campaigned on a policy of territorial expansion. After becoming president he used diplomacy and military force to implement his policy. In this episode we talk with Dr. Amy Greenberg about the politics and strategy of the Mexican-American War. Greenberg is a professor of history at Penn State University and the author of the book A Wicked War: Polk, Clay, Lincoln, and the 1846 U.S. Invasion of Mexico.