Paul Ernst Fackenheim
Paul Ernst Fackenheim (born February 8, 1892 in Frankfurt am Main) was a  German Jewish Army lieutenant who fought in World War I and received the Iron Cross 1st and 2nd class. In 1939 he was detained and transferred to Dachau concentration camp; he was prisoner number 26336. In 1941 Fackenheim was recruited by the Abwehr to serve as a spy; the German Military Intelligence Service appealed to his officer's sense of honour to serve his country once again as a spy in Palestine. His job as a spy in the Middle East lasted only a few days; he was detained and interrogated by the British, who kept him in captivity until 1946. He survived the war as one of the few Jews to be freed from a concentration camp by the German authorities and returned to Germany, settling in Henstedt-Ulzburg

Michael Bar-Zohar wrote his biography, titled in English "Hitler's Jewish Spy"

References 

http://www.nytimes.com/1985/12/29/books/the-jew-who-spied-for-th-nazis.html
http://www.renewamerica.com/columns/sharpe/111208
http://www.nationalarchives.gov.uk/catalogue/displaycataloguedetails.asp?CATLN=6&CATID=8331692&SearchInit=4&SearchType=6&CATREF=KV+2%2F1163

1892 births
Abwehr personnel of World War II
Dachau concentration camp survivors
Jewish collaborators with Nazi Germany
German Jewish military personnel of World War I
German prisoners of war in World War II held by the United Kingdom
Year of death missing
Recipients of the Iron Cross (1914), 1st class