Overseas Contingency Operations Funding: Background and Status [Updated January 15, 2019] [open pdf - 2MB]
"This report provides background information and potential oversight issues for Congress on warrelated and other international emergency or contingency-designated funding since FY2001. [...] This CRS [Congressional Research Service] report is meant to serve as a reference on certain funding designated as emergency requirements or for Overseas Contingency Operations/Global War on Terrorism (OCO/GWOT), as well as related budgetary and policy issues. It does not provide an estimate of war costs within the OCO/GWOT account (all of which may not be for activities associated with war or defense) or such costs in the DOD base budget or other agency funding (which may be related to war activities, such as the cost of health care for combat veterans)."
CRS Report for Congress, R44519
Congressional Research Service: https://crsreports.congress.gov/