In 1943, with World War II raging, a petite 17-year-old was among a team of Soviet agents credited by Moscow with thwarting a Nazi plot and saving the lives of the "Big Three" Allied leaders.

By helping to uncover Operation Long Jump -- drawn up by Adolf Hitler's henchmen to assassinate or abduct U.S. President Franklin Roosevelt, British Prime Minister Winston Churchill, and Soviet Premier Joseph Stalin during a strategy summit in Tehran -- the Armenian-born Goar Vartanyan essentially saved the Allied war effort, according to Soviet sources.

Historians and subsequent evidence have cast considerable -- many say overwhelming -- doubt on the veracity of what its alleged SS mastermind later described as a figment of a bunch of "hacks'" imagination.

But Vartanyan, known as Anita, rose along with her husband and fellow spy, Gevork Vartanyan, to become one of the U.S.S.R.'s most prominent and enduring espionage success stories.

Vartanyan died in Moscow on November 25, taking to the grave the secrets of the purported foiling of Operation Long Jump and her several decades of life as a highly decorated KGB spy.

Russia's Foreign Intelligence Service (SVR) reportedly this week said that the Vartanyans had been involved in "active intelligence work" in "extreme conditions in many countries," without providing any details.

Gevork Vartanyan once boasted that only "2 to 3 percent" of the information about him and his wife had reached the public.

Theirs was a marriage of dedicated anti-fascists and Soviet spymasters, by those mostly Soviet accounts.

Born in Gyumri, in what is now Armenia, in January 1926, Goan reportedly moved with her family to Iran in the 1930s before meeting Gevork Vartanyan in Tehran.

The intervening years are etched -- whether credibly or not -- in Soviet history.

Soviet sources claimed she had joined his anti-fascist group when she was just 16. Four years later, they were married.

The pair reportedly returned to the Soviet Union in 1951.

Goar and Gevork worked undercover together for 30 years in Europe, Asia, and the United States, Russian intelligence has claimed.

"I helped my husband a lot at work, I participated in secret operations. Together we shared failures and joys," she recalled years after Gevork's death in a 2015 interview with Russian state news agency RIA Novosti.

Russian reports said Goar retired as a Soviet spy in 1986 but continued to train young agents.

She and her husband's identities were disclosed in 2000, earning them fame and public accolades in post-Soviet Russia.

Their work inspired an award-winning Soviet-French-Swiss film, Teheran 43, that featured French actor Alain Delon.

London-based espionage historian Alexander Vassiliyev is among those who say the Vartanyans' fame was built on KGB fiction.

"It's a KGB myth that was published after the war was over," he was quoted by RFE/RL's Radio Farda as saying of Operation Long Jump. "So far, no evidence has been obtained that would point to Nazi preparations for assassinations in Tehran."

He added: "Many historians believe that Stalin spread the rumors about the Tehran terror operation to become close to Roosevelt and diminish Churchill's influence."

Still, in 2007, Churchill's granddaughter Celia Sandys met Gevork Vartanyan in Moscow and thanked him for having saved her grandfather's life. At the meeting, Vartanyan, who died in 2012, reportedly raised a glass of Armenian brandy to "the great troika -- Stalin, Churchill, and Roosevelt," adding, "It is thanks to them that we live in peace today."

Goar Vartanyan, who received the Order of the Red Banner in 1984, will be buried at Moscow's prestigious Troyekurovskoye Cemetery later this week.

The Kremlin paid tribute to her on November 27, according to Reuters, saying her career may have changed the course of history. "Without Goar Vartanyan and her husband, Gevork, the history of our world could have been different. These are people who left their mark on the history of mankind," Kremlin spokesman Dmitry Peskov told reporters.

He added that Russian President Vladimir Putin, who himself served as a KGB officer in East Germany in the late Cold War, had expressed his condolences to Vartanyan's family and relatives.

"Putin knew both Goar and her husband well.... Goar visited Putin in the Kremlin, Putin visited her as a guest," Peskov told reporters.