From the Document: "Seventeen years have passed since the U.S. initiated major military operations following the September 11, 2001, terrorist attacks. In the intervening period, operations first classified as 'Global War on Terror' (GWOT) and later 'Overseas Contingency Operations' (OCO) have varied in scope. Though primarily focused on locations in Afghanistan and Iraq, they have also included territories throughout Central and Southeastern Asia, the Middle East, and Africa. This In Focus summarizes major expenditures on U.S. war operations, reconstruction assistance, troop levels and casualties, and ongoing issues for Congress. This analysis narrowly defines war/non-war costs as 'OCO-designated appropriated funds' associated with overseas operations as designated in DOD's official 'Cost of War (CoW)' report. Other observers may define war operations or costs more broadly (see 'Issues for Congress' section)."
CRS In Focus, IF11182
Congressional Research Service: https://crsreports.congress.gov/