The history of warfare is filled with individuals whose acts of betrayal profoundly affected both their own era and the way history remembers them. Turning against one’s country or military allegiance is seldom a simple decision, often shaped by a complex blend of personal ambition, political ideology, resentment, revenge, or ego. Yet even after changing sides, defectors are frequently viewed with distrust, since those willing to betray one allegiance are often suspected of being capable of doing so again.
This overview explores several of history’s most notorious military traitors, beginning with the turmoil of the American Revolutionary War and examining the lasting consequences their actions produced.
Benedict Arnold
Benedict Arnold is one of the biggest, most well-known military traitors on our list. He was a brave and brilliant officer in the Continental Army during the US Revolutionary War. After proving his worth on a number of occasions and receiving brutal injuries, he felt other officers were taking some of the credit for his achievements and being favored over him for promotions.
Even though he was highly trusted by George Washington, Arnold became disillusioned with his side of the war. He defected to the British in 1780, after offering to hand over West Point, in return for a position as a general in the British Army. The British never captured West Point, but Arnold did betray the Continental Army, fighting against those he once led as a brigadier general.
In the United States today, Benedict Arnold’s name is synonymous with the word “traitor.”
Alfred Redl
Alfred Redl, the second individual on our list of military history’s biggest traitors, was the head of the counterintelligence branch in the Austro-Hungarian Army, having pioneered counterespionage techniques. Between 1903-13, he secretly worked as a spy for the intelligence service of the Imperial Russian Army, using his position to hand over extremely valuable documents.
Over the course of his spying career, Redl gave the Russians the entire Austrian invasion plan for Serbia, military plans, doctrines, tactics and strength. He also used his position to provide the names of agents working as spies against Russia. Even worse, he sent some into Russia, only to then inform Russian authorities of their presence.
Redl is believed to be responsible for the deaths of tens of thousands of Austrians during the First World War, and he’s thought to have been part of the reason behind Austria-Hungary’s poor military performance during the conflict. In 1913, he was outed as a spy using his own techniques, at which point he took his own life.
Mildred Gillars
Mildred Gillars, better known by the nickname “Axis Sally,” became one of the most notorious Americans to broadcast Nazi propaganda during World War II. Born in Portland, she relocated to Dresden in 1934 to pursue music studies and later worked as an English teacher. Her decision to collaborate with Nazi broadcasting efforts after the war began shocked many of her friends and relatives back in the United States.
By 1940, Gillars was employed by German State Radio, where she hosted several propaganda programs aimed at Allied troops. One show, Home Sweet Home Hour, attempted to stir feelings of homesickness among American soldiers. Other broadcasts, including GI’s Letter-box and Medical Reports, emphasized battlefield casualties in an effort to spread fear and lower morale. Another program, Midge at the Mike, promoted anti-Semitic rhetoric, attacked President Franklin Roosevelt, and encouraged defeatist sentiment.
Gillars continued broadcasting until just two days before Germany’s surrender in 1945. After the war, authorities located and arrested her in March 1946. She was charged with eight counts of treason, ultimately convicted, and ssentenced to 10-30 years in prison along with a $10,000 fine. She was later released on parole in 1961.
Harold Cole
Harold Cole, notorious for a life marked by petty crimes, theft, and deceit, is remembered as one of Britain’s most infamous and impactful military traitors. During the early stages of World War II, he collaborated with the French Resistance, helping soldiers and downed pilots escape to England via secret routes in German-occupied France.
Initially respected within these circles, Cole ultimately betrayed his comrades to the Gestapo in late 1941. In a devastating act of treachery, he revealed the identities of 150 people involved in the escape networks or aiding the French Resistance. Tragically, approximately 50 of them were executed or died in concentration camps.
Throughout the war, Cole became a target of pursuit by British, German, and French authorities. His life ended violently in 1946 when he was killed during a shootout with French police while resisting arrest.
He’s remembered as one of the “most selfish and callous traitors who ever served the enemy in time of war.”
Robert Hanssen
Considered “possibly the worst intelligence disaster in US history,” Robert Hanssen’s actions as a traitor are the most recent on our list. He served as an FBI agent from 1976-2001, during which he spent much of his career selling highly classified information to the Soviet Union and, after its collapse, to Russia.
Hanssen shared details about American spy technology, including radar systems and surveillance satellites, and exposed the identities of agents who were spying on the Soviets. Additionally, he alerted the USSR about a highly-secret FBI eavesdropping tunnel constructed beneath the Soviet Embassy.
At one point, Hanssen was assigned to uncover a mole within the FBI. Unknown to his superiors, the mole was actually him, which allowed him to successfully conceal his activities. He managed to stay under the radar throughout his career, and it wasn’t until February 18, 2001, after an extensive investigation, that the FBI identified him as a spy and arrested him.
On June 5, 2023, Hanssen, aged 79, was discovered unresponsive in his cell at the ADX Florence supermax prison in Florence, Colorado. He was later pronounced dead, with an autopsy confirming that his death was caused by colon cancer.
Fritz Duquesne
Arguably the most unique military traitor on this list, Fritz Duquesne – better known as “The Duke” – was the leader of a German spy ring during the Second World War. A South African who’d fought for the Boers during the Second Boer War, he served as a secret agent for the Germans during both World Wars, conducting sabotage and gathering evidence in several Allied countries – in particular, the United States, the United Kingdom and South Africa. He was also active in South America.
During the First World War, Duquesne operated a spy ring that targeted British merchant vessels in South America. Prior to the US entering World War II, he operated a spy ring on American soil, made up of 33 German agents. Their covert activities were later revealed to the US government by a double agent.
Throughout his life, Duquesne operated under several aliases and was arrested on numerous occasions, managing to escape from the majority of the facilities he was sent to. He also served as an adviser for US President Theodore “Teddy” Roosevelt and found work in both the publishing and film industries.
Wang Jingwei
Concluding our survey of history’s most infamous military traitors is Wang Jingwei, a prominent leftist politician in pre-Communist China and a long-standing rival of Chiang Kai-shek.
During World War II, Wang struck a controversial alliance with Imperial Japan, surrendering control of Nanjing in return for heading a Japanese-supported puppet government. He openly praised Japan in public statements and used his authority to legitimize, and even promote, collaboration among Chinese citizens with the occupying forces. Wang passed away shortly before the conflict drew to a close.
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Following Japan’s surrender, Chiang Kai-shek’s forces swiftly retook Nanjing and moved decisively to obliterate Wang Jingwei’s legacy. His tomb was demolished, his remains exhumed and cremated, and any form of official commemoration was erased. Presently, the location is marked solely by a simple pavilion inscribed with an unambiguous statement: he was a traitor.