During WWII, a B17 is shot down over germany and the crew is taken prisoner. The navigator, upon his landing after parachuting out of the airplane, breaks both his legs and one arm.
After a few weeks, one of his legs becomes infected. Therefore, he asks for it to be cut it off. After the amputation, the navigator asks the Gestapo to send his leg back home to his base. They agree and do it.
A few weeks later, they have to do the same to his other leg. Once again, he asks them to send his leg back home to his base. They comply.
Another week later, his arm gets infected and he asks for them to amputate again. They say, "Nein!! we can no longer do this for you!"
THe navigator is a bit perplexed and asks, "why?"
They reply, "Because, we think you are trying to escape!"