The United States Joint Forces Command

United States Joint Forces Command was the only combatant command focused on the transformation of U.S. military capabilities. USJFCOM was a functional command that provided specific services to the military.

The commander of USJFCOM oversaw the command’s four primary roles in transformation – joint concept development and experimentation, joint training, joint interoperability and integration […]

USJFCOM developed joint operational concepts, tested those concepts through rigorous experimentation, educated joint leaders, trained joint task force commanders and staffs, and recommended joint solutions to the Army, Navy, Air Force and Marines to better integrate their warfighting capabilities.

(Source)