The United States prefers to fight in coalitions, and has made this clear in both word and deed. Most of the key American national security or defense strategies, such as the Quadrennial Defense Review report or the National Security Strategy, of the last decade or more note this fact. In practice, the United States worked diligently and tirelessly to construct and maintain coalitions of the willing in both Iraq and Afghanistan. American political and military leaders did this-and will continue to do this for future conflicts-because coalition allies provide both political legitimacy at home and abroad for broad national security policies and specific military operations, and because coalition partners help to shoulder security burdens. For these reasons, it seemed appropriate and necessary to address the role that allies play today and might continue to play in American national security formulation and implementation during an era of change for the U.S. military, and for the U.S. Army in particular.