Surveying the expanding conflict in Europe during one of his famous fireside chats in 1940, President Franklin Roosevelt ominously warned that "we know of other methods, new methods of attack. The Trojan horse. The fifth column that betrays a nation unprepared for treachery. Spies, saboteurs, and traitors are the actors in this new strategy." Having identified a new type of war--a shadow war--being perpetrated by Hitler's Germany, FDR decided to...