That's what the Geneva convention is for: to protect the rights of prisoners of war, whether they are Americans or Germans.
7 seconds sound clip from the Stalag 17 movie soundboard.
You can hear this line at 01:13:18.544 in the Blu-ray version of the movie.
Quote context
[...]
- How long is temporarily? I trust not until July.
- Here you see a typical meal the prisoners are getting.
- Schulz, what are we having today?
- Bean soup mit ham hocks. Would you like to taste it?
- Where's the ham hock? There should be a ham hock!
- When you find it, we'll send it to Geneva.
- Are there any complaints? Please speak up. Don't be afraid to talk.
- It's all right, considering.
- What happened to you? Were you beaten? Why don't you answer? What did you do to this man?
- Nobody beat me. We were playing pinochle. It's a rough game.
[...]