Alan Wolfe is professor of political science and director of the Boisi Center for Religion and American Public Life at Boston College. He is author and editor of more than 20 books, including, most recently, Political Evil: What It Is and How to Combat It.

...[F]or all his dreams of glory, Kim Jong Il was no Hitler. And the decidedly ignominious, if not pathetic, way that once powerful leaders in North Africa and the Middle East lost their power should remind us it is one thing to run corrupt and oppressive regimes -- and another entirely to deploy an astonishingly powerful military apparatus in the service of world conquest and the elimination of an entire race of people. The hawkishly inclined want us to believe that the United States cannot have an enemy unless he is deemed to be a carbon copy of the bad guy against whom the good war was fought. But Hitlers, thankfully, are rare....

Unlike today's nasty characters, the totalitarian leaders of the 1930s and 1940s threatened our way of life for two main reasons. Nazism and communism offered an alternative to liberal democracy that, at least for a time, attracted significant numbers of people to its ranks. In addition, those in control of such regimes -- brutal tyrants at home -- were also determined expansionists abroad: Hitler had designs on as much of Europe as he could grab, and Stalin was prepared to take the rest. Were anything like totalitarianism to occur again, we should intervene wholeheartedly to stop it and exhaust every avenue to help those determined to overthrow it.

But nothing like totalitarianism can or will happen again. The dictatorships of the 1930s were the product of a series of unique historical forces coming together in remarkable fashion to make political extremism possible. There was, first and foremost, the violent stalemate known as World War I, which encouraged conspiracies and raised the possibility, in both Germany and Russia, of violent destruction. The rapid inflation of the 1920s convinced Germans that the end was nigh and the subsequent Great Depression contributed to popular unrest everywhere. Germany, like the Soviet Union, was a recently formed state with uncertain borders. Ideological opposites, Hitler and Stalin desperately needed each other: Each justified his rule by stoking fears of other totalitarian dictators in the vicinity....

Hitler and Stalin comparisons direct our attention to the past. However, the world then so little resembles the world of today that history is a particularly unhelpful place to look for answers. Three challenges that U.S. foreign policy will face in the future make it especially inappropriate to look back to the age of the dictators....