The character of Carl Mayer is based on Carl Szokoll, who became involved in ‘Operation Valkyrie’, the failed plot to kill Hitler on July 20th 1944, led by Claus Schenk Graf von Stauffenberg. Szokoll organised the Vienna aspects of this plot and escaped detection in the round-up that followed by the skin of his teeth, even being promoted to major.
Later, he masterminded ‘Operation Radetzky.’ This involved making contact with the Russian forces approaching Vienna in April 1945, and undermining the German defence of the city which he felt would result in unnecessary destruction. The plot was discovered and his co-conspirators, Major Karl Biedermann, Lieutenant Rudolf Raschke and Second Lieutenant Alfred Huth, were caught and hanged from lamp posts in Floridsdorf as the Russians assaulted the city. Szokoll again escaped detection. He was briefly detained by the Russians who thought he was an American spy. After the war he married his half-Jewish fiancée, Chrstl Kukula, and made films.