Jahn was one of the original people assigned by Schulte Stratthaus, before Hitler annexed Austria in 1938. Stratthaus had been appointed by Hitler in 1936 to locate and buy paintings Hitler had painted from 1907 to 1912, and 1921 to 1922. Jahn spent nearly four years tracking down Hitler's early works, until he was called into military service. Jahn became the Art Consultant to the German Embassy in Vienna in 1937, where he would then search for, purchase and collect individual pieces of Hitler's art, in order to allegedly destroy a majority of the paintings. Jahn sold one of the largest collections of Hitler's art, about 18 pieces, with an average selling price of $50,000.