After Max Shachtman's minority split in 1940, served as editor of 'Fourth International' monthly theory/polemical journal of the Socialist Workers Party (SWP) between 1940–45, until displaced by E R Frank (Bert Cochran) on the maneuvers of James P Cannon and the SWP majority who opposed his views on perspectives for European Trotskyists at the mid-war point. He was one of 18 SWP leaders, including the party's National Secretary, James P. Cannon, imprisoned under the Smith Act during the Second World War.