This document is Field Manual 3-39.40, which provides guidance for commanders and staff on internment and resettlement operations. It addresses detainee operations across the spectrum of conflict, from traditional enemy prisoner of war operations to broader detainee operations. The manual describes the doctrinal foundation, principles, and processes that military police and other elements will employ when dealing with internment populations such as U.S. military prisoners and detainees, as well as resettlement operations focused on dislocated civilians. Military police conduct internment and resettlement operations during various types of military operations. The manual standardizes terminology and operational concepts to align with changes in today's operational environments.