Mad Dogs and Servicemen - S3-E13
Frank: Corporal Travis, Richard. To Tokyo. Typical psycho case, shell shock.
Trapper: Frank, that's straight outta World War One! Nobody thinks shell shock anymore.
Frank: Oh, what's the diff? Too much action gets them in the old brain box; makes even the best soldier gaga.
Trapper: Frank, I defy you to show me a medical book that lists the word 'gaga'.
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