 Complete the following phrase:  In 1920 he joined the Independent Social Democratic Party of Germany: he then joined the Communist Party of Germany in 1922. Between 1920 and 1924 he undertook a succession of jobs in various places, at one stage working as a miner at Hindenburg in Oberschlesien as Zabrze had been renamed in 1915. In 192223 he was actively involved in opposition to 