The federal government's growing fiscal challenges underscore the importance of DOD employing a strategic approach to determining the appropriate mix of its military, civilian, and contractor personnel to perform its mission, and determining the functions that are critical for the department to achieve its missions. A committee report accompanying the National Defense Authorization Act for Fiscal Year 2013 directed GAO to assess the measures DOD is taking to balance its workforce against its requirements. GAO examined (1) historical and projected workforce trends, (2) the actions DOD has taken to determine an appropriate workforce mix, (3) the analysis DOD performs to identify core or critical functions, and (4) how DOD used its inventory of contracted services to inform budget submissions. GAO performed trend analysis to determine historical and future workforce levels. GAO also reviewed relevant statutes, DOD and military department guidance, and budgetary submissions, and interviewed officials from DOD and the Office of Management and Budget (OMB).