FORT EUSTIS, Va. -- Members of the U.S. Army Training and Doctrine Command team continue to work toward not only shaping the Army of 2020, but also the Joint Force of 2020 when they participated in a joint planning exercise in Okinawa, Japan, April 29 through May 11.

Hosted by the Third Marine Expeditionary Force staff, the planning exercise provided an opportunity for participants from the Marines, Army, Navy and Air Force to look at real-world plans using the recently published Army-Marines Gaining and Maintaining Access Concept, or GMAC.

"Our participation provided an outstanding practical application of concepts such as the Joint Operational Access Concept, the Air-Sea Battle Concept and the Army-Marine Corps Gain and Maintain Access Concept," said Bill Rittenhouse, chief of the Army Capabilities Integration Center's Joint Interdependency Coordination Division.

Complementary to Air-Sea Battle, GMAC, which was officially signed by the Army and Marine Corps in March, is a key component to the overarching Joint Operational Access Concept, which was published in January by Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey.

"The Joint Force must have the capability to gain and maintain access across any domain," Dempsey wrote in a blog post following the JOAC's release. "The JOAC will chart a path to ensure Joint Force 2020 can provide the military options our nation needs."

In addition to discussing key ideas from the Army-Marine Corps concept, Rittenhouse said exercise participants from Pacific Command, the 7th Fleet, Marine Corps Combat Development Command, U.S. Army Pacific Command, 13th Air Force and a representative from the Air-Sea Battle Office in Washington, D.C., also discussed ideas for the upcoming Joint Concept for Entry Operation, or JCEO, which will replace GMAC as a joint concept.

Although concepts from GMAC will still be applicable to the Army and Marines, the JCEO, its successor, will also incorporate concepts from the Navy and Air Force.

"What this does is it helps the services lay out some very approaches for using the kinds of capabilities that each service requires," Rittenhouse said.

Joint writing teams, including ARCIC's Joint and Army Concepts Division and Concept Development and Learning Directorate, began meeting in March to discuss and begin drafting the JCEO, and the joint concept is estimated to be completed sometime in 2013.