This book, which is a fundamental study of the history of the Russian Orthodox Church of the 20th century, sets out the church history of modern times from Orthodox historical and theological positions and gives an analysis of the most important phenomena and processes. The events of church life and its current problems are considered in the context of general civil history with the wide involvement of documentary materials (including unpublished ones). One of the goals of the book is an attempt to analyze the spiritual causes of the catastrophe that occurred with our country after 1917.