I traced my grandfather on the ICRC which placed him in a POW in Germany in 1918. However, I've now received copies of other documents, in my grandfather's own hand, which state he was never at a proper prisoner of war camp and certainly was not in Germany. He was held in Belgium and was moved around quite a bit but not that far afield. At the Armistice the German officers told them they would be taken to Germany, so it's possible some documentation ended up there but not my grandfather himself - he did in fact escape so perhaps they lost track of him!
So take care - not everything you discover may be correct!
CHMrels