By David G. Perkins and James M. Holmes General David G. Perkins is the Commanding General of U.S. Army Training and Doctrine Command. General James M. Holmes is Commanding General of Air Combat Command. T he mission of the Department of Defense (DOD) is to provide the military forces needed to deter war and to protect the security of the Nation. To accomplish this mission, the various Services within DOD—individually and collectively—must be trained and ready today, while simultaneously preparing for evolving threats in the future. Historically, each Service (the Army, Marine Corps, Navy, Air Force, and Coast Guard) has pursued separate and unique conceptual approaches to the dual requirements of deterrence and protection. These differences have been based largely on each Service’s primary operational domain—the limitations and opportunities presented by operating on land, on the sea, and in the air. We would then try to synchronize a series of federated solutions, developed so...