This document is a report on the 2006 Quadrennial Defense Review conducted by the Department of Defense. It examines how the department has transformed since 2001 to address the new strategic environment characterized by uncertainty, surprise, and non-state threats like terrorism. The review found that the department needs to maintain a sense of wartime urgency, better fuse intelligence and operations, and ensure everything contributes to joint warfighting. It also identified a shift in emphasis from the threats and approaches of the 20th century to the challenges of the 21st, including more proactive and preventative postures.