How can I find out more about WW2 refugee records?

Sheldon asked:


My grandfather was captured by the Nazi’s ion WW2 and taken to a camp at around aged 15 after which he fell in to the hands of the Americans (I’m guessing it would be the army but to be honest we’re not quite sure).

Obviously, there must be records in reference to these sort of activities but does anyone know how I can locate refugee records? Where would be a good place to start looking?

BRAM