RING OF SPIES: How MI5 and the FBI Brought Down the Nazis in America

In 1935-37 America passes several Neutrality Acts, vowing never again to take sides in a European conflict. In 1938 public attitudes changes, with the American people beginning to favor Britain and turn against Germany. One reason was the tip-off received by the FBI on the eve of WWII, which led to the exposure of a Nazi spy ring operating in America.