 On 13 June 1940, Hitler authorized Posee to travel to the Netherlands, where he had to compete with Alfred Rosenberg's ERR organization (see below), Kajetan Mühlmann, Hermann Göring's art curator Walter Andres Hofer and Göring himself in claiming works by Dutch masters, many of which had been purloined, expropriated or confiscated by various Nazi agencies on a number of grounds.Posse went to Poland around November 1940 to examine expropriated artworks there, some of which had been looted by the German Army from museums, palaces and country homes.All of the country's artworks in the German-occupied areas were then cataloged by SS officer and art historian Kajetan Mühlmann, who had done the same previously in Vienna.