My grandfather, now deceased, was held captive in a PoW camp somewhere in or around Italy, and I'd like to try and collate as much documented info on him as I can.
The International Committee of the Red Cross in Geneva is the official repository for all POW reports, from all nations. If you write them, they have a search capability and may be able to give you some information, though in my experience it may take a LOONNNG time for them to respond. If they can find him in their records, they should have the date and location of his capture, the nation which caught him, and the location of any POW camps he was in, as well as information on his ultimate disposition. The following website claims to have a search function as well (for US POWs): http://www.worldvitalrecords.com/indexinfo.aspx?ix=usa_wwii_pow1941-1946