The area that would become Transnistria was organized into the Ukrainian SSR in 1919, under which the Moldavian Autonomous Soviet Socialist Republic (MASSR) was created in 1924. Under Stalinist rule, the Polish community would decline further. After a brief initial period of liberalization and freedom towards Poles in the Soviet Union were subject to harassment, dispersal and mass terror. This trend increased in the late 1930s, as a result of the 1937-8 Polish Operation of the NKVD as well as the ceasing of educational instruction in the Moldavian ASSR for all non-Romanians populations in their native languages which was replaced by Ukrainian and Russian.