Between 1933 and 1945, when both Hitler and Stalin were in power, their two regimes murdered some fourteen million people in the lands between Berlin and Moscow, which I call the Bloodlands.This region then fell into shadow. Because the lands where Hitler killed during the war—Poland, Ukraine, Belarus, the Baltics, western Russia—all became part of Stalin's empire thereafter.I argue that the killing in the Bloodlands is the central event of the twentieth century. My book is its history.