William G. Sebold (; March 10, 1899 – February 16, 1970) was a German-born United States citizen who was coerced into becoming a spy when he visited Germany after being pressured by several high-ranking Nazi members. He informed the American Consul General in Cologne before leaving Germany and became a double agent for the FBI. With the assistance of another German agent, Fritz Joubert Duquesne, he recruited 33 agents that became known as the Duquesne Spy Ring. In June 1941, the Federal Bureau of Investigation arrested all of the agents. They were convicted and sentenced to a total of 300 years in prison.
Early life
Sebold served in the German army engineering corps during World War I. After emigrating to the United States in 1922, he married and worked in industrial and aircraft plants throughout the United States and South America. Renken was in fact Major Nickolaus Ritter of the Abwehr.
Ritter gave Sebold final instructions before he left for the United States including shortwave radio codes and the use of microphotographs. Sebold was given the alias "Harry Sawyer",
Sebold was tasked to meet with various spies, pass along instructions to them from Germany, receive messages in return, and transmit them back in code to Germany. The intention was to pull off the efforts of spies who were passing technological secrets to the Germans during World War II.
Contacts U.S. consulate
Before leaving Germany, Sebold visited the U.S. Consulate in Cologne, Germany, and insisted on speaking with the Consul General. He told the Consul that he had been blackmailed into becoming a German spy but that he was a loyal American citizen and wanted to cooperate with the Federal Bureau of Investigation (FBI) in the United States. The U.S. government agreed.
Sebold sailed from Genoa, Italy, and arrived in New York City on February 8, 1940. There, Sebold (with secret help from the FBI) set himself up as a consulting diesel engineer, with an office in Times Square in Manhattan. The spies came to the office to deliver blueprints, wartime information, and other sensitive information regarding the United States. However, the office was outfitted with hidden microphones and two-way mirrors, so FBI agents would be able to film the meetings for future use. Using the office, the FBI were able to obtain countless hours of incriminating footage. For example, the group's leader Fritz Joubert Duquesne was caught discussing how fires could be started at industrial plants to slow production, and showed photographs of blueprints for a new bomb being built in the United States. In different footage, a spy explains his plan to bomb a building, going as far as bringing dynamite and detonation caps to Sebold's office.
thumb|right|upright=1.6|Mugshots of Duquesne Spy Ring members. In his office and with cameras secretly rolling, Sebold met with a string of Nazis who wished to pass secret and sensitive national defense and wartime information to the Gestapo. In the United States, Duquesne had been a [[New York Herald journalist and was the "master coordinator" of the Nazi spies operating in the United States. He contacted aircraft and other technology companies and requested information that he claimed he would use for his lectures. Any plans or photos that he received were sent to the Wehrmacht.
At their first meeting, Duquesne was extremely worried about the possibility of listening devices in Sebold's office. He gave Sebold a note suggesting that they should talk elsewhere. After relocating to an automat, the two men exchanged information about members of the German espionage system with whom they had been in contact.