Karl Krenn, who had a doctorate in prehistoric history, worked from 1932 at the Naturhistorisches Museum in Vienna. He started as a research assistant and rose to become a curator in 1943 in charge of the prehistoric history department, temporarily for some years, and then on a permanent basis from 1950. Prior to this he had earned a reputation as an air raid warden, helping to extinguish fires in the museum building. He was not a member of the NSDAP, and after the war he was entrusted with securing scholarly material from the apartments of museum employees who had been forced to flee and to hand it over to the police. It is unclear, however, whether and how conscientiously he performed this work. Having become unable to work on account of his health, he retired in 1952. He was the subject of provenance research, since he had given twenty-three prints to the Österreichische Galerie between 1944 and 1946.