During the civil war in Russia the community decreased as a result of famine and disease. Under the Soviet regime the Ashkenazi Jewish population dropped to 429 and the Krymchak Jews - to several hundred. In the early 1920s the Krymchaks begun migrating to the larger towns of Crimea, mainly to Simferopol and Kerch. In 1926 the Krymchak population of Karasubazar stood at 1,042, comprising 16.3 of the total Krymchak population of Crimea. In 1932 three Jewish farm settlements in the county had a population of 149 Jewish families. In 1939 there were 429 Jews in Karasubazar; the 471 Jews in the County comprised 1.42 percent of its total population.
About 250 Jews managed to leave the town and another 20 to leave the County before the German occupation, which began on November 1, 1941. 62 Ashkenazi Jews and 468 Krymchaks were registered by the Germans. The latter appointed an elder for the Ashkenazi community. The Ashkenazi Jews were ordered to appear at the town administration offices, supposedly to be sent to work. On December 10, 1941 76 Jews were taken to an anti-tank trench near a hatchery in the town and shot to death. On January 17-18, 1942 468 Krymchak Jews from Karasubazar and the surrounding settlements were asphyxiated in gas vans and buried outside the town. The few remaining Jews (artisans apparently kept alive temporarily to fill German labor needs) were shot later.
Karazubazar was liberated by the Red Army on April 14, 1944. In 1945 it was renamed Belogorsk.