That was actually the Arizona National Guard.
Perhaps so as to which service supplied the extras, equipment, etc. But the actors in the command post scene (remember the colonel’s exagerrated pronunciation of “Three?”) had sateen utility uniforms with USMC shirt pocket emblems. QED, the ANG soldiers are Marines.
BTW, the comment was meant to be tongue-in-cheek and is certainly done fairly as my 23 years of service were all USMC.