This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
By the end of the 1920s, Soviet authorities had closed every Adventist journal and made evangelization illegal, the opening moves in a campaign that grew far harsher in the decade that followed. Through the 1930s, as Stalin's collectivization drive brought mass political repression across the Soviet Union, the Leningrad congregation and almost all Adventist communities in the USSR were dissolved outright and most of the church's leaders were arrested.
The suppression fell on the officially registered Seventh-day Adventist church itself, not only on the smaller unregistered splinter, the True and Free Adventists, who continued meeting underground through the same years. Remarkably, the central All-Union Council of Seventh-day Adventists remained officially in existence even as the congregations under it were dissolved on the ground, a gap between formal standing and lived practice that defined Soviet religious policy of the period.
No precise year narrower than the decade itself is recorded for how many communities fell, and no reliable casualty count survives either: a specific figure near 150 ministers and more than 3,000 members repressed circulates in the Adventist Church's own historical accounts, but it has not been verified against a primary source. What the 1930s repression changed for Adventism's spread in the Soviet Union was near total, from an organized registered presence to communities scattered, arrested and driven into hiding within a single decade.