Hm, I seem to remember something from the Army:
General Order #1Yeah, I know the Marines have different general orders — but I'd bet that [or functionally similar] is in them.
I will guard everything within the limits of my post and quit my post only when properly relieved.
It was really a situation of two armed and stupid individuals with really fortunately poor marksmanship skills. We had several bullet-riddled Quonset huts but nobody hit. Hopefully, the two of them left the Corps soon afterward.
While I'm into my "while I was a PFC" stories, I stood guard at that same ammo dump in the hills of Camp Pendleton on Christmas Eve 1965 - about a month before deploying to Vietnam. In those days, we stood guard in our Service Dress Alpha (Greens) uniform with Barracks Cover, overcoat, cartridge belt and an M-14. On that late Christmas Eve, for the first time in my entire life, it snowed (I'm from Southern California). It was beautiful and I was fascinated with it. About an inch or so accumulated, so I made a snowball of some of it and as the light of the dawn of Christmas morning began, I was "putting" that ball of snow with my M-14 rifle butt when a large black car arrived at my post. I came to attention as the Commanding General, Marine Corps Base Camp Pendleton stepped out of the car and I hurriedly presented arms. He walked up to me and said "what were you doing?" and I said "Golf, Sir?". He gave me a glare and said "Merry Christmas, A__hole". and got back into his car and left.
Ah, the memories!