A letter report issued by the Government Accountability Office with an abstract that begins "The Department of Defense (DOD) is required by law to conduct a comprehensive examination of the national defense strategy, force structure, modernization plans, infrastructure, and budget every 4 years including an assessment of the force structure best suited to implement the defense strategy at low-to-moderate level of risk. The 2006 Quadrennial Defense Review (QDR), completed in February 2006, represents the first comprehensive review that DOD had undertaken since the military forces have been engaged in operations in Iraq and Afghanistan. GAO was asked to assess (1) the strengths and weaknesses of DOD's approach and methodology for the 2006 QDR and (2) what changes, if any, in the QDR legislation could improve the usefulness of the report, including any changes that would better reflect 21st century security conditions. To conduct its review, GAO analyzed DOD's methodology, QDR study guidance, and results from key analyses and also obtained views of defense analysts within and outside of DOD."