Visible crew/equipment: At the end, after Father Mulcahy says goodbye to Sarah, when it cuts to a wideshot we can see two actors' rubber T-marks on the ground. The first is behind Father Mulcahy's feet, a white T-mark (albeit dirty) where Sarah had been standing, and the second becomes visible when Klinger runs over and bumps into Kellye, he kicks up some dirt which causes the black rubber T-mark to flip up off the ground.
Continuity mistake: When the red head woman is playing the piano, it's a double. In the close up her hair is back and you can see her face. In the wide shots her hair covers her face so as to conceal the switch.
Visible crew/equipment: When Marina arrives in the chopper with the wounded, the array lighting rig is reflected on the chopper's windshield.
Visible crew/equipment: When a very tired Hawkeye's in post-op checking on Marina in the morning, the shadow of the boom mic can be seen on the window curtain at the top, right corner of the screen.
Visible crew/equipment: After the troupe's performance in post-op, when it cuts to Brandy in Margaret's tent we can see the boom mic dipping into view at the top, right corner of the screen.
Factual error: When Winchester is shown in the Post Op, his oak leaf and medical symbols are on the wrong lapels.
Continuity mistake: As Potter pours the drinks for himself and Brandy, the glasses have enough for a sip. In the close up, they're a quarter to half full.
Continuity mistake: In Potter's tent, he holds the door for Brandy to enter. In the close up, you see him drop his left hand to close the door after she passes him and inside. After the angle change, his hand is back on the door, and she's just even with him walking forward.
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