6.The Rosenbergs gave atomic secrets to the Soviets

Julius and Ethel Rosenberg were part of a spy ring that funneled vital US atomic information to the Soviets, who were racing to build a bomb of their own in the 1940s. The couple was also able to turn Ethel's brother David Greenglass, who was working on the Manhattan Project. The secrets they revealed were said to have sped up the progress of the Soviet arms race by several years. The Rosenbergs, along with co-conspirator Morton Sobell, were tried and convicted of espionage on March 29, 1951, and sentenced to death. (Sobell served 17 years, and Greenglass made a deal to testify against his sister to save his wife.)

7.Juan Pujol tricked Hitler about the D-Day invasion

A Spanish farmer, Juan Pujol, was perhaps the greatest double agent ever. He had a passionate hatred for Adolph Hitler, but since Spain was neutral in World War II, he had no direct way to fight the Nazis. That's when he dreamed up a scheme to visit Germany and convince the Nazis to take him on as a spy, and then turn over any information to the Allies. Pujol's ploy was a success — both sides eventually recruited him. One of his most significant contributions was with D-Day. He worked in tandem with the MI5 to convince Hitler that the impending Allied invasion at Normandy was going to take place at Calais. Because of this trickery, Hitler held back several panzer divisions and ensured the success of the attack, saving thousands of lives.

8.Sidney Gottlieb brought LSD to the CIA

One of the most notorious American spies in the Cold War orchestrated mind control experiments on US citizens. In the 1950s and 60s, Sidney Gottlieb was in charge of a secret CIA project called MK-ULTRA and conducted experiments on the possibility of mind control. Gottlieb was a strong advocate for LSD and under his direction, many people were unwittingly dosed with the drug and their reactions observed. One was Army officer Frank Olson, who ended up committing suicide nine days later. The program was exposed in the 1970s, but Gottlieb was exonerated and given a medal of honor. He died at the age of 80 in India, after having retired there.

9.Hermann Gortz was Nazi spy who parachuted into Ireland

One of the Third Reich's most notorious spies was Hermann Gortz, who lead a couple of failed missions. The first was in 1936, when he was arrested in Britain after sketches of an air force base were found in a house he was renting; he was jailed for four years and deported back to Germany. Afterward, he devised a scheme to parachute into Ireland and hope to convince the IRA to side with the Nazis. The first part of the plot was successful — he landed in a field in Ireland in 1940 and established contact. However, a raid by the Irish Police uncovered the plot and Gortz went into hiding for 18 months. He was captured and held in Ireland throughout the war. In 1947, when faced with being deported back to Germany to stand trial for war crimes, he took a cyanide pill and died instantly.

10.Belle Boyd was a spy for the Confederate Army

Maria "Belle" Boyd was a Southerner who spied on the Union during the American Civil War. Relying on her Southern charm, she infiltrated Union soldier camps and was able to glean valuable information. In one famous episode, she ran on foot to Major General Thomas J. "Stonewall" Jackson's brigade to give him last minute information before an attack. Belle was arrested several times and finally incarcerated in Washington D.C. but never gave up her love for the Confederacy, hanging the Confederate flag in her cell and sending messages to her supporters with a bow and arrow. After her release, she wrote several memoirs and toured the US, marrying twice and dying in poverty in 1900.