Historical analogies to current events can be illuminating, but dangerous. Even if strong similarities exist, difference do too, and therefore caution is required when using them. This is especially true with analogies to Naziism and Hitler. Argudendo ad Hitlerum is fraught with peril, and is used far too cavalierly. Hillary found out about the perils when she compared Putin’s incursion into Ukraine-and yes, Crimea is Ukraine-to Germany’s actions in 1936-1938: the occupation of the Rhineland, the Anschluss, the taking of the Sudetenland, and the eventual seizure of the rest of Czechoslovakia. Her remarks unleashed a storm of criticism. Mark this...