U.N., the Night and the Music - S11-E10
Continuity mistake: When Col. Potter runs out of his tent to say goodbye to Capt. Lal, he wears only one slipper. When the jeep drives away and Potter's feet once more are visible, both feet are in slippers. (00:22:05)
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