Daniel L. Byman is a nonresident senior fellow with the Saban Center for Middle East Policy at the Brookings Institution. He also directs the Security Studies Program and the Center for Peace and Security Studies at Georgetown University's Edmund A.Walsh School of Foreign Service. His books include Deadly Connections: States that Sponsor Terrorism (Cambridge, 2005). Kenneth M. Pollack is a senior fellow in Foreign Policy Studies at the Brookings Institution, where he is research director for the Saban Center. He is author of The Persian Puzzle:The Conflict between Iran and America (Random House, 2004) and The Threatening Storm:The Case for Invading Iraq (Random House, 2002).