A Jewish spy dropped behind enemy lines, where he infiltrates the Nazis? If that sounds like the plot of "Inglorious Basterds", that's because... it is.
It is also the life of Frederick Mayer, who was born in Germany, emigrated to the US, and enlisted in the American Army following Pearl Harbor. Mayer, who was obviously fluent in German, was paratrooped into Austria, where he impersonated a Nazi officer. He was able to relay all kinds of important information to the allies.
After some success, Mayer was sold out by a contact, caught and imprisoned. (In a strange turn of events, the Nazis discovered he was Jewish by examining his, ahem, circumcision, but decided that no Jew would be crazy enough to do what Mayer did. Stupid Nazis!)
The war was nearing its end, and the Germans started to realize that they are not winning this one. So the German armies at Innsbruck negotiated their surrender... with Mayer as an intermediary. This as he was still a POW.
After the war, Mayer came back to America, where he lived until the ripe age of 94.