The Soviet authorities annexed the town on September 22, 1939. In the spring of 1940, the refugees from western Poland were obliged to register with the authorities and to declare whether they wished to take up Soviet citizenship or return to their former homes, now under German occupation. Jewish communal life was forbidden, and Zionist leaders were forced to move to other cities to keep their past activities from the knowledge of the authorities. By 1941 the Jewish population had increased to over 15,000 including over 4,000 refugees.