 From 1915 until 1917, he served in the German Army during World War I. in 1917–18 he played at the Fronttheater in Mitau.In 1919 he was brought to the Deutsches Theater in Berlin by Max Reinhardt.From his extensive theatrical work, his role as "Mackie Messer" ("Mack the Knife") in the world premiere of Bertolt Brecht's "The Threepenny Opera" is particularly noteworthy.