What did both sides do with deserters who entered their lines? These really were not prisoners in the normal sense. They often were a good source of information about the enemy. Sending them off to a prisoner of war camp would discourage future deserters from entering your line. Still I am not sure they could simply be allowed to wander about. If they were considered prisoners were they exchanged back to the enemy? Keeping them around would require feeding and clothing them so probably something had to be done with them.