Rear echelon. A veteran of any branch, having served in country, but not on the front lines.
Joe: "I served in Vietnam. I have a service medal to prove it. But, I was, 'in the rear (with the beer)' the whole time. That was fine by me. I didn't want to go out there." (laughs)
Disabled Veteran: "You were a 'wing wiper'! A 'wing wiper'!! Do you think you are any expert?!"
A term used to describe a member of the US Air Force
Probably comes from the Air Force's reputation for being neat and orderly.
Did ya see that wing-wiper over there? Bet I could arm wrestle him.