Since 2001, the Department of Defense (DoD) has received about $2.2 trillion to supplement the base-budget funding provided in its regular, annual appropriations—amounting to about 20 percent of DoD’s appropriations over that time. Almost all of that sum has been designated for overseas contingency operations (OCO) that began after 9/11.

In CBO’s estimation, since 2006, an average of more than $50 billion per year (in 2019 dollars) of the funds designated for OCO has been used to support enduring activities rather than the temporary costs of overseas operations. In this report, CBO analyzes how DoD’s funding for military conflicts has changed over time and how OCO funding affects perceptions of DoD’s spending and the anticipated costs of the department’s plans.

Read the report