I was thinking either a radio operator or gunner on a bomber.
Radio Operator would be smart, a little bit of the 40's version of a geek, and saw the army as a way to learn about the new techs.
Gunner would be an adrenaline junky (Wanted to to fly fighters, but couldn't afford school), thinks America should've gotten into the war before getting suckerpunched at Pearl Harbor (Hindsight 20/20, of course.