When you sign up you write a blank check with only your signature on it. Uncle decides how much to cash it in for later. For some it's for all.
I was in for the cold war so I have this ringing in my ears, a messed up lower back and two screwed up knees; all in all, a small check. And even though it wasn't a "war" in 1982, I still saw friends go home in boxes so when the time came and we felt the landing gear thunk up into the 747 at Rhine-Main, it was a relief and a joy.
I'd still do it all over again, silly me. But I absolutely hate it when anyone "thanks" me for my service.