Continuity mistake: Margaret is shampooing Frank's hair; she raises her foam covered hands to allow him to kiss her. The camera angle changes and her hands are nearly foam-free. (00:03:25)
Continuity mistake: When the General comes up, Pierce and Trapper are walking away toward the camera's left. When Pierce calls for the General's attention he is shown gesturing to the open door. Problem is, that they should be looking over their left, not right, shoulders, and we should see the inside, not outside, of the door.
Continuity mistake: The crew is getting the bad news in Henry's office when Radar reports more choppers. From behind, Henry starts to react, and when the angle changes he reacts again.
Continuity mistake: While talking to Hildebrandt, Henry smacks his hands together while saying "Gee, whiz!" When the angle changes, his hands are on the desk.
Continuity mistake: Usually when you see Pierce, his hair is parted on the left side. When he is nibbling on the nurse's neck in the Swamp, his hair is parted on the right. Then the next time he's seen, it's parted on the left again.
Answer: Even an Army field hospital would have SOME weapons for self-defense if the enemy attacked. What's meant is that it's not a combat outfit, and therefore wouldn't have enough weapons to actually attack anyone. (It's also mentioned a few times that the Officer of the Watch is supposed to carry a pistol at all times, but Hawkeye refuses to do it when he's in charge and Colonels Blake and Potter don't enforce the rule).
Captain Defenestrator