Schwerin was discharged from the army in 1920. He spent the following two years engaged in a managerial business apprenticeship with a coffee import firm in Bremen, and a petroleum company in Berlin. In 1922 he rejoined the Reichswehr as a professional soldier, being commissioned with the rank of lieutenant into the Prussian Army's Infantry Regiment No.1. In 1931 he joined Infantry Regiment No.18 in Paderborn. He was promoted to captain in June 1933. From 1933 to 1935 he attended the General Staff course at the Prussian Military Academy in Berlin.