I'd guess it would have a lot to do with the war we were talking about. I'd guess in WW II any air crew of a bomber would see their friends spread all over the inside of their bomber. Navy had their huge losses to Kamikaze's in the pacific. Foot sloggers are always on the sharp point.

I saw a study once on public tv about a researcher who determined the best way to minimize PTSD or combat fatigue was to make sure that the guys/gals that were fighting around you you knew and trusted and had very strong bonds with. That is say a combat division trains together, goes over seas together, fights together, pulls out to rest and then gets replacement. So the men/women have time to make that strong bond with their squad. One, variable anyway.

In the current environment where the navy, and air force are more detached from the fighting . . . and I hope I don't step on anyones toes . . . they are probably less likely to develop PTSD.

Speaking for myself, I was on a ship that landed marines and army units on beach assaults, and the firefight on shore, the bombardments, the bombing by the F-4, and the threat of Cong sappers mining the ship kept my attention I can tell you.