Bloodlands: Europe Between Hitler and Stalin. By Timothy Snyder. Basic Books; 524 pages. IN THE middle of the 20th century Europe’s two totalitarian empires, Nazi Germany and Stalin’s Soviet Union, killed 14m non-combatants, in peacetime and in war. The who, why, when, where and how of these mass murders is the subject of a gripping and comprehensive new book by Timothy Snyder of Yale University. The term coined in the book’s title encapsulates the thesis. The “bloodlands” are the stretch of territory from the Baltic to the Black Sea where Europe’s most murderous regimes did their most murderous work. The...