"The Sword in the Clouds" is a semi-fictional account of the Condor Legion, a German military unit that participated in the Spanish Civil War on the side of the Nationalists. The book, while claiming to be a factual account, has been criticized for its pro-Nazi propaganda and its portrayal of the Spanish Civil War.
It's important to note that Zehren's writing was heavily influenced by the Nazi ideology, and his works should be viewed in that context. He was a member of the Nazi Party and his writing reflected the party's propaganda agenda.
While "The Sword in the Clouds" is his most well-known work, Zehren wrote several other books, including:
* "Die weisse Garde" (1938)
* "Soldaten der Nacht" (1940)
* "Das Reich der Sterne" (1943)
Zehren's works have been criticized for their historical inaccuracies and their pro-Nazi propaganda. However, they are still studied today as examples of the literature produced during the Nazi era.