Feigning to be an asset of the German Abwehr, he passed off disinformation to Germany as part of the British Double-Cross System while occasionally using cover as a diplomat for the Yugoslav government-in-exile in London.

He held a great aversion to Nazism, and in 1940, infiltrated the Abwehr, Germany's military intelligence service, which considered him a valuable asset due to his business connections in France and the United Kingdom.

Deceptions in which he participated included Operation Fortitude, which sought to convince German military planners that the Allied invasion of Europe would take place in Calais, not Normandy, thereby diverting hundreds of thousands of German troops and increasing the likelihood that Operation Overlord would succeed.

[6] When Popov was an infant, the family left Titel and permanently relocated to their summer residence in Dubrovnik, which was their home for much of the year.

In November 1918, Austria-Hungary disintegrated into a number of smaller states, and its Balkan possessions were incorporated into the Kingdom of Serbs, Croats and Slovenes (renamed Yugoslavia in 1929).

The newly established, Serb-led state was plagued by political infighting among its various constitutive ethnic groups, particularly Serbs and Croats, but also Hungarians and Germans.

[6] Popov's father indulged his sons, building a spacious villa by the sea for their exclusive use where they could entertain their friends and host expensive parties.

Popov's father subsequently enrolled him at Lycée Hoche, a secondary institution in Versailles, which he attended for the following two years.

[14] "Women ... found him irresistible," Times columnist Ben Macintyre writes, "with his easy manner, loose, sensual mouth ... and green ... bedroom eyes.

Germany had only recently come under the rule of Adolf Hitler and the Nazi Party, but at the time, Popov paid little regard to politics.

Germany was already the site of mass book burnings, the first concentration camps had been established and the systematic persecution of Jews had commenced.

"Duško despised Nazism," biographer Larry Loftis writes, "and since he wasn't German, he believed he owed no allegiance to Hitler or the state.

[22] Two weeks later, Jebsen returned to Belgrade, and informed Popov that he had joined the Abwehr, German's military intelligence service, as a Forscher (researcher).

Hope enrolled Popov as a double agent with the codename Scoot (he was later known to his handler as Tricycle), and advised him to cooperate with Jebsen.

[citation needed] Popov was famous for his playboy lifestyle, while carrying out perilous wartime missions for the British.

They both shared a mission at Casino Estoril, and it is believed that Popov served as inspiration for the character of James Bond in Fleming’s novels.

During a televised interview, Duško Popov related having informed the FBI on 12 August 1941 of the impending attack on Pearl Harbor.

[28] When Jebsen was arrested by the Gestapo in Lisbon, the British feared Popov had been compromised and ceased giving him critical information to pass along to the Germans.

In 1972, John Cecil Masterman published The Double Cross System in the War of 1939 to 1945, an intimate account of wartime British military deception.

In 1974, Popov published an autobiography titled Spy/Counterspy, "a racy account of his adventures that read like a James Bond novel."

Several of the events described in the book were either entirely fictional, such as a fistfight Popov claimed to have had with a German agent, exaggerated for dramatic effect, or could not be substantiated through subsequently declassified intelligence records.

[34] Shortly after Popov's death, MI6 began declassifying documents that pertained to Allied intelligence-gathering and disinformation activities during the war, thereby verifying many of his claims.

He was the subject of a one-hour television documentary produced by Starz Inc. and Cinenova, titled True Bond, which aired in June 2007.