Hey there. George C. Marshall held the title of "Army Chief of Staff", which is basically a Joint Chiefs of Staff position on the United States Military High Command. There are 4 Joint Chiefs of Staff:
-Chief of Staff of the Army
-Chief of Staff of the Army
-Chief of Naval Operations
-Commandant of the Marine Corps
-Commandant of the Coast Guard (not really)
They are led by the Chairman of Joint Chiefs of Staff (CJCS)