This Army Techniques Publication (ATP) manual provides basic doctrinal discussion on the organization and operations of the Army Field Support Brigade. The primary target audience for this field manual includes: Headquarters Department of the Army, Army commands, theater armies, direct reporting units, and supported units at all levels. ATP 4-91 applies to the Active Army, Army National Guard (ARNG)/Army National Guard of the United States (ARNGUS) and the US Army Reserve (USAR) unless otherwise stated. The proponent for this manual is the US Army Training and Doctrine Command. The approving authority is the Commander, United States Army Combined Arms Support Command (USACASCOM) and Sustainment Center of Excellence. The technical review authority is the US Army Materiel Command.