system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are there Laws of War? Why do they follow rules when they're battling to the death.

Why do war crimes exist?
gpt
1. Eventually the war will be over. If you are still alive but you committed war crimes, you may be punished.

2. Some things are so horrible that neither side wants them used, because then *both* sides will lose. Example: nukes.

3. Some things are so horrible that they will convince neutral countries to join the struggle against you.

4. You want the enemy to treat your prisoners and civilians decently, so you do the same -- knowing that if you stop the decency, they may stop too.