These units provided services to the fleet such as air combat training and enemy electronic warfare simulation support.
The U.S. Marines received their first F-4Bs in June 1962, with the VMFA-314 Black Knights at MCAS El Toro, California becoming the first operational squadron.
Marine Phantoms from the VMFA-531 Gray Ghosts arrived in Vietnam on 10 April 1965, flying close air support missions from land bases as well as from USS America.
Marine F-4 pilots claimed three enemy MiGs (two while on exchange duty with the USAF) at the cost of 75 aircraft lost in combat, mostly to ground fire, and four in accidents.
The purpose of this particular training units was to provide Fleet Marine Force (FMF) squadrons with F-4 Phantom-qualified aircrew and maintenance personnel.