Aid Station - S3-E19
Continuity mistake: After Hawkeye and Trapper finish their toast to the Ritz Brothers, they toss their glasses over they shoulders. Trapper's flips in a lazy arc, and Hawkeye's in a flatter arc. When Radar is at the door, the glasses hit the door at a much higher speed and shatter.
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