On 6 September 1939, after the invasion of Poland by Nazi Germany, Berman followed government directions for "able-bodied men" and took a train going in the eastern direction.Lucyna Tychowa and Andrzej Romanowski, Tak, jestem córką Jakuba Bermana [Yes, I'm the Daughter of Jakub Berman], p. 38. He went to Białystok, occupied by the Soviet Union after the Soviet invasion of Poland. With his friend Alfred Lampe, Berman was active in Polish-communist circles there and became a Soviet citizen. In March 1941 he moved to Minsk, where he worked as an editor at Sztandar Wolności ('The Banner of Freedom'), a Polish-language bulletin published by the Communist Party of Byelorussia. Berman's doctoral dissertation, written under the direction of Krzywicki and entitled O strukturze miast polskich na podstawie spisu ludności w 1791 r. ('On the structure of Polish cities based on the population census of 1791'), was brought to Białystok by his friend and colleague Irena Sawicka, but burned in Minsk when a dormitory where Berman and other journalists were housed was bombed by the Germans.Lucyna Tychowa and Andrzej Romanowski, Tak, jestem córką Jakuba Bermana [Yes, I'm the Daughter of Jakub Berman], pp. 51–55.
