1. Eddie Chapman: The crook turned WWII spy who double-crossed the Nazis

Born in England in 1914, Chapman did a brief stint with the British army as a teen then turned to crime, becoming a professional safecracker. In 1939, he was arrested on the island of Jersey and sentenced to prison. While he was behind bars, World War II broke out and the Germans seized Jersey. When Chapman was released in 1941, he offered to spy for the Germans but was ignored. Not long after, he was arrested again and sent to a Nazi-run prison on the outskirts of Paris. There, the Germans took Chapman up on his offer and eventually trained him as an agent for the Abwehr, the Third Reich’s military intelligence organization. In late 1942, after parachuting into England on a mission to blow up a De Havilland aircraft factory north of London, Chapman instead offered to work for MI5, the British intelligence agency. In January 1943, the British faked an attack on the De Havilland factory and successfully tricked the Germans into thinking Chapman had done his job. For his supposed bravery, the Nazis awarded him a medal. In 1944, Chapman, codenamed Zigzag by MI5, parachuted into England once again, this time on a mission to let the Germans know whether their missiles were reaching their targets. Instead, he gave the Nazis misleading information, causing them to redirect the attacks to less populated areas and likely saving numerous lives.

After the war, Chapman smuggled gold and ran a health spa, among other activities. He died in 1997.

2. William Sebold: The FBI counterspy who brought down a German espionage ring

Sebold, a German native born in 1899, served in his nation’s army during World War I then lived in the United States and South America before becoming a naturalized U.S. citizen in 1936. Three years later, during a visit to his homeland, Sebold was recruited to spy on the United States for Germany. The Nazis, who had learned he once worked briefly at an airplane factory in California, threatened him if he failed to cooperate. Sebold secretly went to the American consulate in Cologne and reported what had happened. Back in the United States in February 1940, the FBI convinced Sebold to become the agency’s first counterspy, or double agent. The FBI constructed a shortwave radio station on New York’s Long Island, where agents impersonating Sebold exchanged hundreds of messages with the Nazis. The FBI also helped Sebold set up a specially rigged office in Manhattan, where agents clandestinely filmed him meeting with German spies, including Frederick Duquesne, head of a Nazi espionage network in America.

In June 1941, as a result of Sebold’s work, the FBI arrested 33 people accused of spying for the Nazis. All 33 members of what became known as the Duquesne Spy Ring were convicted that December, shortly after Germany declared war against the United States. By then, Sebold and his wife had entered a witness protection program. He died in California in 1970.

3. Juan Pujol García: The operative who fooled the Nazis about D-Day

Before his remarkable espionage career, Pujol, a Barcelona native born in 1912, cycled through a series of occupations, including failed chicken farmer, owner of an unsuccessful movie theater and manager of a rundown hotel. After the outbreak of World War II, Pujol, who despised Adolf Hitler, volunteered his services to British authorities in Madrid but was rejected. Pretending to be a rabid Nazi, he then offered to spy for the Germans, believing this would help convince the British to take him on. After being trained by the Abwehr, Pujol agreed to establish a network of agents in the United Kingdom who could supply the Germans with military intelligence. However, instead of going to England, Pujol went to Portugal, where he invented an espionage ring that eventually included more than two dozen agents, all of them completely fabricated. Using reference books and magazines, Pujol, who had never been to England, devised fictional intelligence reports that looked as if he were sending them from London. Meanwhile, he continued to offer to spy for the British, who in the spring of 1942 finally agreed to let him work as an operative and brought him to England, where he was given the code name Garbo because he was such a good actor. Agent Garbo’s greatest deception came in 1944, when he played a key role in Operation Fortitude, a successful plot to mislead the Nazis into thinking that the bulk of the D-Day troop landings would occur at Calais rather than Normandy.

After the war, Pujol moved to Venezuela, but in 1949 British authorities seeking to protect him from possible Nazi retribution told his ex-wife and children that he’d died of malaria in Africa. However, decades later a British historian tracked down Pujol, still in Venezuela, and in 1984, the 40th anniversary of D-Day, the public learned he was still alive. He was honored at Buckingham Palace and reunited with his children before passing away in 1988.

4. Harold “Kim” Philby: The high-ranking British intelligence officer who was a KGB mole

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Getty Images / J. Wilds/Keystone

The son of an Englishman who was an explorer and writer, Philby was born in India in 1912 and educated at elite schools in Britain. He became interested in communism as a university student and by the mid-1930s had been recruited to spy for the Soviets. At the urging of his Soviet handlers, Philby worked as a journalist then joined MI6, the British intelligence agency, during World War II. In 1944, he became head of the agency’s anti-Soviet intelligence operations, all the while passing secrets to the KGB. Five years later, in 1949, he was made the MI6 station chief in Washington, D.C., where he served as the main liaison between British and American intelligence agencies.

In 1951, two of his friends and fellow British operatives defected to Moscow after Philby warned them they were about to be exposed as double agents. Philby was suspected of tipping them off but MI6 officials stood by their charming colleague and no charges were brought against him. In the wake of the scandal, Philby resigned from MI6; however, the agency later rehired him and in 1956 sent him to Beirut, where as a cover he again worked as a journalist. Then, in early 1963, after learning British officials had discovered convincing new evidence he’d spied for the Soviets, Philby escaped to Russia. He died there in 1988 and received a funeral with a KGB honor guard as well as other tributes including his own postage stamp.

5. Denis Donaldson: An Irish Republican Army member murdered for being a British spy

As a young man, Donaldson, who was born in Belfast in 1950, joined the Irish Republican Army (IRA) and fought against British rule in Northern Ireland. In the 1970s, he went to prison for plotting to bomb several buildings and served time with Gerry Adams, the future leader of Sinn Fein, the IRA-linked political party, as well as Bobby Sands, the famous Irish hunger striker who died in 1981. Sometime during the 1980s Donaldson became a paid spy for Britain and went on to work for British intelligence services while at the same time becoming a key Sinn Fein official. In 2002, police in Belfast arrested Donaldson and accused him of being part of a Sinn Fein spy ring at the Northern Ireland parliament building, Stormont, where he served as Sinn Fein’s senior administrator. However, in December 2005, the charges against Donaldson were mysteriously dropped. Soon afterward, he publicly confessed to being a longtime informant for the British and said he’d been recruited “after compromising myself during a vulnerable time of my life.” Following this announcement, Donaldson fled to an isolated cottage in County Donegal. It was there in April 2006 that he was found tortured and shot dead. In 2009, a splinter group called the Real IRA claimed responsibility for Donaldson’s murder, but no charges have been filed in the case.

6. Robert Hanssen: The FBI agent who became one of the most damaging moles in U.S. history

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A Chicagoan born in 1944, Hanssen earned degrees from Knox College and Northwestern University before joining the FBI in 1976. Three years later, he volunteered to spy for GRU, the Soviet military intelligence agency. In 1980, after Hanssen’s wife reportedly caught him with some suspicious-looking papers, he admitted to selling secrets to the Soviets but claimed the information he’d handed over was worthless. At his wife’s insistence, Hanssen promised to cut ties with the Soviets and confessed to a priest, who told him to donate the ill-gotten money to charity. In 1985, though, he resumed spying for the Soviets, this time for the KGB, while continuing to rise through the FBI’s ranks. In 1991, with the Soviet Union dissolving, Hanssen stopped spying out of fear he’d be found out. However, in 1999, while serving as the FBI liaison to the U.S. State Department, he started spying for the SVR, the Russian intelligence service. After the FBI learned, thanks to help from an ex-KGB officer, that Hanssen was a mole, he was arrested in February 2001. Later that year, in an effort to avoid the death penalty, the veteran FBI agent pleaded guilty to 15 counts of espionage.

During his two decades as a spy, Hanssen handed over thousands of pages of classified material that revealed such things as the identities of Soviets spying for the United States, specifics about America’s nuclear operations and the “continuity of government” plan (detailing where top U.S. government officials will be moved to in a national emergency), the existence of an FBI-built tunnel underneath the Soviet Embassy in Washington, among numerous other national security secrets. Why Hanssen, a church-going father of six, betrayed his country is not fully known, although money rather than ideological beliefs seems to have been one motivating factor. For his efforts, Hanssen was paid $600,000 in cash and diamonds, with another $800,000 supposedly held for him in a Russian bank. He is currently serving his term of 15 consecutive life sentences at the supermax prison in Florence, Colorado.