Duquesne Spy Ring

The Duquesne Spy Ring is the largest espionage case in United States history that ended in convictions. A total of 33 members of a German espionage network headed by Frederick "Fritz" Joubert Duquesne were convicted after a lengthy investigation by the Federal Bureau of Investigation (FBI). Of those indicted, 19 pleaded guilty. The remaining 14 were brought to jury trial in Federal District Court, Brooklyn, New York, on September 3, 1941; all were 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 agents who formed the Duquesne 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 opened a restaurant and used his position to get information from his customers; another worked on an airline so that he could report Allied ships that were crossing the Atlantic Ocean; others worked as delivery people so they could deliver secret messages alongside mundane ones.