Continuity mistake: When Henry, Trapper, and Hawkeye get into the jeep with Radar notice the style of jeep and its number is 16930382, but when they're driving to the chopper pad the style differs - things such as hood, antenna, etc, and its number is 11172419. Then when the chopper takes off the jeep's style is back to the original jeep they were in.
Continuity mistake: As Henry watches the chopper fly off, his back is to Radar's jeep. After he orders back to camp, Henry is suddenly standing with his right side to the jeep without having turned.
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