The new book from the “100 Greats” series is devoted to a number of mysteries of domestic and world history of the 20th and early 21st centuries. Sometimes it seems that a century that has only recently sunk into oblivion gives us more reasons for thought and material for research than all the past centuries and millennia of human history. Two world wars, many local military conflicts, revolutions and civil wars, conspiracies, putschs and coups, economic “miracles” and severe crises, outstanding cultural achievements and great scientific discoveries, the ups and downs of the human spirit - all this fit into a relatively short chronological period . The reader is offered original versions, the results of research by scientists, local historians, and journalists.