Born in Cape Colony, South Africa, on September 21, 1877, and naturalized a citizen of the United States in 1913, Fritz Joubert Duquesne was a Captain in the Second Boer War and later a Colonel in the Abwehr, Germany’s division of military intelligence.

A native of Germany, Edmund Carl Heine went to the United States in 1914 and became a naturalized citizen in 1920. Until 1938, he held various positions in the foreign sales and Service department of Ford Motor Company and Chrysler Corporation. His employment took him to the West Indies, South America, Spain, and Berlin, Germany. Heine was closely associated with Dr. Hans Luther, former German Ambassador in Washington, D.C., and Prince Louis Ferdinand of Berlin. Around 1938, Heine was recruited to find American automobile and aviation industry secrets that could be passed to Germany through the Duquesne Spy Ring.

Duquesne was captured and imprisoned three times by the British, once by the Portuguese, and once by the Americans in 1917, and each time he escaped. In World War I, he was a spy and ring leader for Germany and during this time he sabotaged British merchant ships in South America with concealed bombs and destroyed several. Duquesne was also ordered to assassinate an American, Frederick Russell Burnham, Chief of Scouts for the British Army, but failed to do so. He was also known as "The man who killed Kitchener" since he claimed to have sabotaged and sunk HMS Hampshire, on which Lord Kitchener was en route to Russia in 1916.

Heinrich Stade went to the United States from Germany in 1922 and became a citizen in 1929. He had been a musician and publicity agent in New York. He told agent Sebold he had been in the German Gestapo since 1936 and boasted that he knew everything in the spy Business.

Axel Wheeler-Hill went to the United States in 1923 from his native Russia. He was naturalized as a citizen in 1929 and was employed as a truck driver.

In 1924, Felix Jahnke left Germany for the United States, where he became a naturalized citizen in 1930. Jahnke had attended military school in Germany and had served in the German Army as a radio operator.

Born in Germany, Hartwig Richard Kleiss went to the United States in 1925 and became a naturalized citizen six years later. Following his arrival in the United States, he was employed as a cook on various ships.

A German native, Paul Scholz went to the United States in 1926 but never attained citizenship. He had been employed in German book stores in New York City, where he disseminated Nazi propaganda.

Else Weustenfeld arrived in the United States from Germany in 1927 and became a citizen 10 years later. From 1935 until her arrest, she was a secretary for a law firm representing the German Consulate in New York City.

Max Blank went to the United States from Germany in 1928. Although he never became a U.S. citizen, Blank had been employed in New York City at a German library and at a book store which catered to German trade.

Erwin Wilhelm Siegler went to the United States from Germany in 1929 and attained citizenship in 1936. He had served as chief butcher on the SS America until it was taken over by the U.S. Navy.

Richard Eichenlaub, who went to the United States in 1930 and became a citizen in 1936, operated the Little Casino Restaurant in the Yorkville Section of New York City. This restaurant was a rendezvous for many members of this spy ring, and Eichenlaub introduced several new members into the group.

In 1931, Franz Joseph Stigler, left Germany for the United States, where he became a citizen in 1939. He had been employed as a crew member and chief baker aboard U.S. ships until his discharge from the SS America when the U.S. Navy converted that ship into USS West Point. His constant companion was Erwin Siegler, and they operated as couriers in transmitting information between the United States and German agents aboard. Stigler sought to recruit amateur radio operators in the United States as channels of communication to German radio stations. He had also observed and reported defense preparations in the Panama Canal Zone and had met with other German agents to advise them in their espionage pursuits. In January 1941, Stigler asked agent Sebold to radio Germany that Prime Minister Winston Churchill had arrived secretly in the U.S. on the H.M.S. King George V with Lord Halifax.

In 1934, Paul Fehse left Germany for the United States, where he became a citizen in 1938. Since his arrival in the United States, he had been employed as a cook aboard ships sailing from New York Harbor. Fehse was one of the directing forces in this espionage group. He arranged meetings, directed members' activities, correlated information that had been developed, and arranged for its transmittal to Germany, chiefly through Sebold. Fehse, who was trained for espionage work in Hamburg, Germany, claimed he headed the Marine Division of the German espionage system in the United States.

A German native, Walischewski had been a seaman since maturity. He became a naturalized citizen in 1935. Walischewski became connected with the German espionage system through Paul Fehse. His duties were confined to those of courier, carrying data from agents in the United States to contacts abroad.

Oberstleutnant (Lieutenant colonel) Nikolaus Ritter led spy rings in the United States, Great Britain, and North Africa from 1936 to 1941. Ritter was born in Germany and had served as an officer in the First World War on the Western Front in France where he was twice wounded. He emigrated to New York in 1924, married an American, and returned to Germany in 1936 to join the Abwehr as Chief of Air Intelligence based in Hamburg operating under the code name: DR. RANTZAU.

He first met Fritz Duquesne in 1931, and the two spies reconnected in New York on December 3, 1937. Ritter also met Herman Lang while in New York, and he arranged for Lang to later go to Germany help the Nazis finish their version of the topsecret Norden bombsight. Ritter achieved several major successes with the Abwehr, most notably the Norden bombsight, in addition to an advanced aircraft auto-pilot from the Sperry Gyroscope Company, and also intelligence operations in North Africa in support of Field Marshal Erwin Rommel. But some of Ritter's recruits became double-agents who catastrophically exposed his spy rings.

Until his arrest, Lang had been employed by the Carl L. Norden Corp., which manufactured the top secret Norden bombsight and other highly confidential materials essential to the national defense of the United States. During a visit to Germany in 1938, Lang conferred with German military authorities, Colonel Nikolaus Ritter of the Abwehr, and he reconstructed the plans of the confidential materials from memory. Ritter then hid the plans in the wooden casing for an umbrella, and, on January 9, 1938, personally handed the umbrella off to a German steward and secret courier on the ship Reliance bound for Bremen.

Born in Vienna, Stein was a Jewish immigrant who had escaped in 1939 with the help of a U.S. diplomat in Vienna, Vice Consul Ogden Hammond Jr. She later met Hugo Sebold, the espionage instructor who had trained william Sebold (the two men were not related) in Hamburg, Germany. She enrolled in this school and was sent to the United States by way of Sweden in 1939.

He arrived on the Heian Maur in Seattle in 1938. On October 19, 1940, Sebold received a radio message from Germany that CARR (Abwehr Agent Roeder) was to meet E. Satoz at a Japanese club in New York.

As the FBI arrested Duquesne and his agents in New York in 1941, Ezima escaped to the West Coast, boarded the Japanese freighter Kamakura Maru, and left for Tokyo. One Historian states that Ezima was arrested for espionage in 1942 and sentenced to 15 years; however, U.S Naval Intelligence documents state that "at the request or the State Department, Ezima was not prosecuted."

Ritter recruited william Sebold who later joined the FBI which resulted in the arrest of the 33 Abwehr agents of the Duquesne Spy Ring. In Great Britain, he recruited Arthur Owens, code named JOHNNY, who became an agent for MI5 (British Intelligence) operating under the code name SNOW. Owens exposed so many Abwehr covert agents operating in Britain that by the end of the war MI5 had enlisted some 120 double agents. Although Ritter was never captured, it was the arrest of the Duquesne Spy Ring that ultimately resulted in Ritter's fall from the Abwehr and his reassignment in 1942 to air defenses in Germany for the remainder of the Second World War.

The 1945 film The House on 92nd Street was a thinly disguised version of the Duquesne Spy Ring saga of 1941.

Roeder entered a guilty plea to the charge of espionage and was sentenced to 16 years in prison. In 1949, Roeder published his book, Formulas in plane triangles.

Upon conviction, Lang received a sentence of 18 years in prison on espionage charges and a two-year concurrent sentence under the Registration Act. Lang was deported to Germany in September 1950.

Duquesne was brought to trial and was convicted. He was sentenced to serve 18 years in prison on espionage charges, as well as a 2-year concurrent sentence and payment of a $2,000 fine for violation of the Foreign Agents Registration Act. He served his sentence in Leavenworth Federal Penitentiary in Kansas, where he was mistreated and beaten by other inmates. In 1954 he was released due to ill health, having served 14 years, and died indigent, at City Hospital on Welfare Island (now Roosevelt Island), New York City on May 24, 1956, at the age of 78.

Impoverished and delusional, he was committed to Napa State Hospital in 1965. Diagnosed with manic-depression, he died there of a heart attack five years later at 70. His life story as a double agent was first told in the 1943 book Passport to Treason: The Inside Story of Spies in America by Alan Hynd.

After World War II, he was assigned to Puerto Rico, where he pinpointed the group behind the assassination attempt on President Harry Truman. Friedemann died of cancer on August 23, 1989 in Stillwater, Oklahoma.