At its heart, the book is a history of the Soviet Union, the most comprehensive reorganization of human society ever attempted by a nation-state. Drawing on much new information, Richard Pipes explains the country's evolution from the 1917 revolution to the Great Terror and World War II, global expansion and the Cold War chess match with the United States, and the regime's decline and ultimate collapse. There is no more dramatic story in modern history, nor one more crucial to master, than that of how the writing and agitation of two mid-nineteenth-century European thinkers named Marx and Engels led to a great and terrible world religion that brought down a mighty empire, consumed the world in conflict, and left in its wake a devastation whose full costs can only now be tabulated.