The FBI's Biggest Case

The Duquesne Spy Ring is the largest espionage case in United States history that ended in convictions. A total of thirty-three members of a German espionage network headed by Frederick “Fritz” Joubert Duquesne were convicted after a lengthy espionage investigation by the Federal Bureau of Investigation (FBI). Of those arrested on the charge of espionage, 19 pleaded guilty. The remaining 14 men who entered pleas of not guilty were brought to jury trial in Federal District Court, Brooklyn, New York, on September 3, 1941; and all found guilty on December 13, 1941. On January 2, 1942, the group was sentenced to serve a total of over 300 years in prison.

The German spies who formed the Duquesne spy ring were placed in key jobs in the United States to get information that could be used in the event of war and to carry out acts of sabotage: one person opened a restaurant and used his position to get information from his customers; another person worked on an airline so that he could report Allied ships that were crossing the Atlantic Ocean; others in the ring worked as delivery people so that they could deliver secret messages alongside normal messages.

William G. Sebold, who had been recruited as a spy for Germany, was a major factor in the FBI's successful resolution of this case through his work as a double agent for the United States government. For nearly two years the FBI ran a radio station in New York for the ring, learning what Germany was sending to its spies in the United States while controlling the information that was being transmitted to Germany. Sebold's success as a counterespionage agent was demonstrated by the successful prosecution of the German agents.

One German spymaster later commented that the ring's roundup delivered "the death blow" to their espionage efforts in the United States. FBI director J. Edgar Hoover called his concerted FBI swoop on Duquesne's ring the greatest spy roundup in U.S. history.

The 1945 film The House on 92^nd Street was a thinly disguised version of the Duquesne Spy Ring saga of 1941, but differs from historical fact. It won screenwriter Charles G. Booth an Academy Award for the best original motion picture story.

http://en.wikipedia.org/wiki/Duquesne_Spy_Ring