Western Ukraine, which included largely the historic region of Galicia, became part of the Soviet Union in 1939. Although Ukrainian, its population was never part of the Russian Empire, but was Eastern Rite Catholic. After the Second World War, the Ukrainian Greek Catholic Church identified closely with the nationalist aspirations of the region, arousing the hostility of the Soviet government, which was in combat with Ukrainian Insurgency. In 1945, Soviet authorities arrested the church's Metropolitan Josyf Slipyj, nine bishops and hundreds of clergy and leading lay activists, and deported them to forced labor camps in Siberia and elsewhere. The nine bishops and many of the clergy died in prisons, concentration camps, internal exile, or soon after their release during the post-Stalin thaw, but after 18 years of imprisonment and persecution, Metropolitan Slipyj was released when Pope John XXIII intervened on his behalf. Slipyj went to Rome, where he received the title of Major Archbishop of Lviv, and became a cardinal in 1965.