Since the September 11, 2001, terrorist attacks, the Department of Defense (DOD) has been engaged in domestic and overseas military operations in support of overseas contingency operations (OCO). These operations include Operation Iraqi Freedom, which focuses principally on Iraq, and Operation Enduring Freedom, which focuses principally on Afghanistan, but also include operations in the Horn of Africa, the Philippines, and elsewhere. Obtaining an accurate picture of OCO costs is of critical importance given the need to evaluate trade-offs and make more effective use of defense dollars in light of the nation's long-term fiscal challenges. In the past, the GAO has reported on the need for DOD to become more disciplined in its approach to developing plans and budgets, including building more OCO costs into the base defense budget. In February 2009, the Office of Management and Budget (OMB), in coordination with the Office of the Secretary of Defense (OSD), developed new guidance for use when constructing the initial fiscal year 2010 OCO funding request that more narrowly defined what should be considered an OCO funding need. The guidance remained in effect for building the fiscal year 2010 OCO supplemental request and the fiscal year 2011 OCO budget request.

Under the Comptroller General's authority, GAO evaluated: 1. The fiscal year 2011 OCO budget request by comparing it to the fiscal year 2010 OCO appropriation and the fiscal year 2010 OCO supplemental request. 2. The assumptions DOD used to create the fiscal year 2010 OCO supplemental request and the fiscal year 2011 OCO budget request. 3. The extent to which the assumptions used for creating the fiscal year 2010 OCO supplemental request and the fiscal year 2011 OCO budget request are sensitive to operational changes. 4. The extent to which DOD moved certain costs of ongoing contingency operations from its OCO budget request into its base budget request.