Bestselling author Bradley Smith reveals the surprisingly rich exchange of wartime intelligence between the Anglo-American allies and the Soviet Union, as well as the procedures and politics that made such an exchange possible.

Between the late 1930s and 1945, allied intelligence organizations expanded at an enormous rate in order to acquire the secret information their governments needed to win the war. But, as Smith demonstrates, the demand for intelligence far outpaced the ability of any one ally to produce it. For that reason, Washington, London, and Moscow were compelled to share...