At the onset of World War II, the Soviet invasion of Poland began on September 17, 1939. The Red Army entered eastern Poland in furtherance of the secret Molotov–Ribbentrop Pact and contrary to the Soviet–Polish Non-Aggression Pact. Tarnopol was captured, renamed Ternopol, and incorporated into the Ukrainian Soviet Socialist Republic under Ternopol Oblast. The Soviets made it their first priority to decimate Polish intelligentsia and destroy Polish culture. Ukrainian nationalist leaders were imprisoned. Mass arrests, torture and executions of Ukrainians and Poles and Jews followed. The Soviets also carried out mass deportations of the "enemies of the working class" to Kazakhstan. In practice, this translated into members of the former state administration, police, border service and land and business owners, Christians and Jews alike.