After the Occupation and annexation of the Baltic states by the Soviet Union in 1940, repression of ethnic Estonians followed. According to Sergei Isakov, almost all societies, newspapers, organizations of ethnic Estonians were closed in 1940 and their activists persecuted. The country remained annexed to the Soviet Union until 1991, except for the period of Nazi occupation between 1941 and 1944. During the era of Soviet occupation, the Soviet government maintained a program of replacing the indigenous Estonians with immigrants from the Soviet Union. In the course of violent population transfers, thousands of Estonian citizens were deported to the interior parts of Russia (mostly Siberia), and huge numbers of Russian-speaking Soviet citizens were encouraged to settle in Estonia. In the Ida-Viru and Harju Counties, cities such as Paldiski, Sillamäe, and Narva were ethnically cleansed and the indigenous Estonian population was totally replaced by Russian colonists. As a result of Soviet occupation, the Russian population in Estonia grew from about 23,000 people in 1945 to 475,000 in 1991, and the total Slavic population to 551,000, constituting 35% of the total population at its peak.