The Quadrennial Defense Review (QDR) was a report stipulated by Section 923 of the National Defense Authorization Act for FY1997 (Public Law 104-201). The QDR was produced every four years from 1997 to 2014 by the Secretary of Defense in consultation with the Joint Chiefs of Staff. The QDR is credited historically with being modeled off the 1993 Bottom-up Review (BUR), which was initiated by Secretary of Defense Les Aspin to serve as a comprehensive review of the nation’s defense strategy, force structure, modernization, infrastructure, and foundations. The first QDR followed this same model to examine the current conditions of national security and prepare for future challenges and opportunities. Section 941 of the National Defense Authorization Act for FY2017 (Public Law 114-328) replaced the QDR with the National Defense Strategy.