In the wake of the 11 September 2001 terrorist attacks on the United States, President George W. Bush designated Iran, along with Iraq and North Korea, as a point on a tripartite “axis of evil” and a threat to U.S. national security. By including Iran in the group, the President signaled a significant shift in U.S. policy toward that country, with important implications for the U.S. military in the years ahead. This paper briefly examines the pertinent history of Iran, focusing on factors influencing its relations with the United States, American policy toward Iran, and relevant U.S. security options for the future. The purpose here is to assess the impact of these developments on the Department of Defense as a whole and the U.S. Army in particular.