This United States Army manual, Army Regulation AR 140-10 Army Reserve Assignments, Attachments, Details, and Transfers July 2021, prescribes policy and procedures for assigning, attaching, removing, and transferring U.S. Army Reserve Soldiers. It defines Ready Reserve Control Groups and the Selected Reserve. Detailed procedures are given for removing Soldiers from an active status. It also gives procedures for inter-Service transfer and selective retention of unit Soldiers. It covers policies, responsibilities, and procedures to assign, attach, detail, remove, or transfer U.S. Army Reserve (USAR) Soldiers.