In the early days of the occupation, the Allies controlled traffic between the zones to manage the flow of refugees and prevent the escape of former Nazi officials and intelligence officers.[17] These controls were gradually lifted in the Western zones, but were tightened between Western and Soviet zones in 1946 to stem a flow of economic and political refugees from the Soviet zone.[18] Between October 1945 and June 1946, 1.6 million Germans left the Soviet zone for the west.[19]