In this startling, intensively researched book, bestselling historian Paul Kengor shines light on a deeply troubling aspect of American history: the prominent role of the "dupe." From the Bolshevik Revolution through the Cold War and right up to the present, many progressives have unwittingly aided some of America's most dangerous opponents. Based on never-before-published FBI files, Soviet archives, and other primary sources, Dupes exposes the legions of liberals who have furthered the objectives of America's adversaries. Kengor shows not only how such dupes contributed to history's most destructive ideology—Communism, which claimed at least 100 million lives—but also why they are so relevant to today's politics.