 He began a relationship in 1923 with Julia Lipschutz (born 1895 or 1905, died after 1984), who became his wife under the name Katia Landau.He defended Leon Trotsky and his positions against those of the party line of the KPÖ and became one of the central figures in opposition to the slowly forming Stalinism.In 1927, he and like-minded colleagues were expelled from the party.