Much of the academic debate surrounding the War on Terror focuses on presidential power after 9/11. In this context, the role of the US Congress in directing the outcome of national security policies is often overlooked. This book illustrates how Congress played a key role in the War on Terror during Barack Obama's presidency. Instead of arguing that Congress was a compliant bystander and incapable of making successful counterterrorism policy, the legislative branch did more than hand the president a blank check. In using an innovative data set on congressional debates and policymaking, the book shows that the interaction between congressional entrepreneurs and senior committee/party leaders determined the outcome of controversial policies, including drone warfare, Guantanamo and the NSA's mass surveillance activities.