Screenplay credits are given to Julius Epstein, James Hamilton and Walter Kelley. Their source material was the 1956 novel "The Willing Flesh" by Willi Heinrich, a fictional work that was loosely based on the true story of Johann Schwerdfeger (1914-2015). The real-life Wehrmacht NCO was a highly-decorated combat veteran who fought through both the Battle of the Caucasus and Kuban pocket.