During the Second Boer War , Burnham and Duquesne had tried to assassinate eachother , but they never met until 1910 in Washington , D.C. Duquesne was arrested twice by the FBI and in 1942 he and 32 other Nazi agents were captured and sent to prison in the largest spy ring case in U.S. history . Duquesne was twice arrested by the FBI and in 1942 he , along with the 32 other Nazi agents who made up the Duquesne Spy Ring , was sent to prison for espionage in the largest spy ring conviction in U.S. history .