This U.S. Army manual, Army Techniques Publication ATP 4-02.55 Army Health System Support Planning March 2020, provides guidance to the medical commander, medical planner, and command surgeon at all levels of command in planning Army Health System support. Users of Army Techniques Publication 4-02.55 must be familiar with unified land operations established in Army Doctrine Publication 3-0; the operations process as stated in Army Doctrine Publication 5-0; how Army forces conduct large-scale combat operations described in Field Manual 3-0; Army plans and orders production as promulgated in Field Manual 6-0; mission command systems of tactical units and the mission command process established in Army Doctrine Publication 6-0; Army Health System support described in Field Manual 4-02; and the Joint Health Services described in Joint Publication 4-02. The principal audience for this publication is all medical commanders, command surgeons, and their staffs, and nonmedical commanders involved in medical planning. Army Techniques Publication 4-02.55 updates Army Health System planning topics while adopting current terminology and concepts as necessary. The Army Health System is a complex system of interrelated and interdependent systems which provides a continuum of medical treatment from point of injury or woundingthrough successive roles of medical care and is inextricably linked to the Military Health System through the Defense Health Agency Role 4 Hospitals for the provision of definitive care as patients are evacuated to continental United States from Role 3 medical treatment facilities in theater. The medical planner is able to provide the best possible Army Health System for all Army operations by carefully applying operational medicine doctrine and principles. The Army Health System provides support to forces deployed across the full range of military operations in all operational arrangements. The Army Health System is a complex system of highly synchronized, interrelated, and interdependent systems comprised of ten medical functions. The medical functions align with medical disciplines and specialty training with the capabilities required to provide state-of-the-art care to Soldiers regardless of where they are deployed or assigned.