The U.S. 81st Infantry Division SSI, or Support Service Instruction, is a military document providing guidelines for support services within the 81st Infantry Division of the United States Army. This division, first activated in 1943 during World War II, has seen service in multiple conflicts, including the Invasion of Sicily and the Battle of Normandy. The SSI outlines the organization, policies, and procedures for various support services such as supply, transportation, maintenance, medical, and others, ensuring efficient and effective support to the division’s combat units during operations.