Factual error: Henry says that every Wednesday, his wife drives up Route 26 with some friends. US. Route 26 starts out in Nebraska and leads to Oregon. The closest thing that could be described as a "Route 26" would be the road leading from Princeton, IL to Dixon, IL which begins 85 miles from Bloomington. The writer probably meant Route 24, which passes about 20 miles north of Bloomington. (00:03:10)
Continuity mistake: In one of the earlier episodes Henry becomes the father of a baby boy; his other two children have been established as Molly and Janey, both girls. In "Abyssinia Henry," Henry get his discharge papers and wanted to call home with the good news. He tells Radar that he will have to wait a while, as his son, Andrew, will be practising his trombone. As Henry only has one son, Andrew has to be the son who was born while Henry was in Korea. Even if Henry was in Korea from the very first days of the war, by the time he left his son can't be any older than 18 months - hardly likely to be playing a trombone.
Factual error: When reminiscing about Radar's appendectomy, Henry says it took a long time to find because it was behind his secum. The appendix is behind the secum in more than 50% of people, so this shouldn't have fooled a doctor of Henry's caliber. (00:09:00)
Continuity mistake: When Henry kisses Margret, she grabs her hat. In the reverse shot, her hand is around Henry's neck. After the next cut, it's on her hat again. (00:20:00)
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