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 fight fire with fire, authorizing the formation of the Office of Strategic Services (OSS) to organize and oversee covert operations. Based on an extensive analysis of OSS records, including the vast trove of records released by the CIA in the 1980s and '90s, as well as a new set of interviews with OSS veterans conducted by the author and a team of American scholars from 1995 to 1997, The Shadow War Against Hitler is the full story of America's far-flung secret intelligence apparatus during World War II. In addition to its responsibilities generating, processing, and interpreting intelligence information, the OSS orchestrated all manner of dark operations, including extending feelers to anti-Hitler elements, infiltrating spies and sabotage agents behind enemy lines, and implementing propaganda programs. Planned and directed from Washington, the anti-Hitler campaign was largely conducted in Europe, especially through the OSS's foreign outposts in Bern and London. A fascinating cast of characters made the OSS run: William J. Donovan, one of the most decorated individuals in the American military who became the driving force behind the OSS's genesis; Allen Dulles, the future CIA chief who ran the Bern office, which he called "the big window onto the fascist world"; a veritable pantheon of Ivy League academics who were recruited to work for the intelligence services; and, not least, Roosevelt himself. A major contribution of the book is the story of how FDR employed Hitler's former propaganda chief, Ernst "Putzi" Hanfstengl, as a private spy. More than a record of dramatic incidents and daring personalities, this book adds significantly to our understanding of how the United States fought World War II. It demonstrates that the extent, and limitations, of secret intelligence information shaped not only the conduct of the war but also the face of the world that emerged from the shadows.