While I don't think that my Marine Corps should be embracing the death cult called islam, your statement is not entirely correct. Every Marine Corps base, or station, has a chapel. Don't know know about synagogues, though.
I don't know about Marines but in the '60s us Army grunts had our religious needs cared for carefully regardless of religion. A multi-use (including Jewish) chapel was the closest building to my basic training Company area. A Protestant Chaplain was assigned full-time to this chapel. Other religious leaders would hold services every appropriate day (Sat or Sun).
Oh, yeah, I forgot about the single Russian Orthodox soldier in my Company. The 1st Sgt simply had to tell him he was SOL.
We had no muzzies but I suspect the 1st Sgt would have had the same message for them at that time.