This publication provides doctrine for the Army Health System (AHS) in support of the modular force. The AHS is the overarching concept of support for providing timely AHS support to the tactical commander. It discusses the current AHS force structure modernized under the Department of the Army (DA)-approved Medical Reengineering Initiative and the Modular Medical Force that is designed to support the brigade combat teams (BCTs) and echelons above brigade (EAB) units. As the Army's AHS doctrine statement, this publication identifies medical functions and procedures that are essential for operations covered in other Army Medical Department (AMEDD) proponent manuals. This publication depicts AHS operations from the point of injury, illness, or wounding through successive roles of care within the area of operations (AO) and evacuation to the continental United States (CONUS)-support base.