This publication provides the capstone doctrine for the Army Health System (AHS) in support of the modular force. The Army Health System is the overarching concept of support for providing timely medical support to the tactical commander. It discusses the current medical 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 and echelons above brigade units. As the Army's capstone medical 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 Army Health System operations from the point of injury, illness, or wounding through successive roles of care within the theater and evacuation to the continental United States (CONUS) support base. It presents a stable body of operational doctrine rooted in actual military experience and serves as a foundation for the development of AMEDD proponent manuals on how the AHS supports the modular force. This publication is for use by commanders and their staffs and command surgeons. It is to be used as a guide in obtaining as well as providing AHS in an area of operations. Information in this publication is applicable to the full spectrum operations. It is compatible with the Army's sustainment and protection doctrine and is in consonance with Joint Publication (JP) 4-02. This publication implements or is in consonance with the following North Atlantic Treaty Organization (NATO) Standardization Agreements (STANAGs), and American, British, Canadian, Australian, and New Zealand (ABCA) Standards and Quadripartite Advisory Publication 256.