It's USAAF Sgt. J.J. Sefton, main character of Billy Wilder's Stalag 17, based on the play of the same name. Sefton is an outcast, but not of his own making. He's made an outsider due to the fact that he doesn't hesitate to trade with the enemy - -a valuable skill he learned after being robbed after his initial arrival.
In the end, he causes the death of the man who betrayed him and his entire bunk, while not really giving a damn about them.
He's one of my favorite fictional soldiers.
*Red*