Three thousand troops are not sufficient to keep even a single U.S. military base in Afghanistan after 2014. This report, released jointly with the Institute for the Study of War, describes how to calculate the force requirements for keeping one single base in Afghanistan after 2014, concluding that it is not possible to do so with fewer than about 6,000 troops. The report identifies many (but not all) of the specific tasks and specialties required to keep an airbase capable of handling large cargo aircraft running and to protect it against known, current enemy capabilities. It also finds that a base manned at such a level would have virtually no ability to advise and assist the Afghan National Security Forces or even to conduct meaningful counter-terrorism operations. The notion of keeping only 3,000 troops in Afghanistan is militarily infeasible.