This book, based on extensive research including in the Russian and Vatican archives, charts the development of relations between the Catholic Church and the Soviet Union from the Bolshevik Revolution of 1917 to the death of Pope Pius XI in 1939. It provides background information on the animosity between the Orthodox and Catholic churches and moves towards reconciliation between them, discusses Soviet initiatives to eradicate religion in the Soviet Union and spread atheist international communism throughout the world, and explores the Catholic Church's attempts to survive in the face of persecution within the Soviet Union and extend itself. Throughout the book reveals much new detail on the complex interaction between these two opposing bodies and their respective ideologies.