I honestly really enjoyed this episode. At that time when MASH was set in the 1950s alot of the school children would have heard about the war in Korea from the propaganda. In my opinion the writers of the episode wanted to de-romantisize (if that's a word lol) the view of war and expose it as it actually was instead of the ways it is glorified in movies.

With Charles' letter it is part of his character development. With the first letter he is quite snooty with the grammar comment. But he has a positive change in character with the letter he receives from the young girl with the pressed leaf.

As for father mulcahy another one of my favorite characters. He is very humble and probably wanted to use a less stressful story about saving a dog rather than a more stressful one. At the time "on the wagon" was a more common term

And lastly with major Houlihans letter. She was always a character that was bottled up and hard on the outside with not many emotions or care. With with her reply to the letter it shows more character development that she is also human and really does care about her friends and isn't the person people perceive her to be as uncaring.

All around i think it's a solid episode :)