The monograph is devoted to the study of the difficult and dramatic period of the Russian Orthodox Church in the period from 1917 to 1945. The author examines the evolution of the relationship between the Church and the authorities from extremely negative (persecution of the Church) to reconciliation and the beginning of the rebirth of the Russian Orthodox Church. The participation of the Church during the Great Patriotic War and its contribution to the victory are considered in detail on the basis of actual examples. The contribution of the Russian Orthodox Church to the victory in the Great Patriotic War is analyzed. Separately, the author examines the history of the Russian Orthodox Church through the examples of specific historical characters: priests, mestablishers, patriarchs.