1. Julius Rosenberg gave Russia plans for nuclear bombs. Julius and Ethel Rosenberg were arrested in 1950 for espionage thought to date back to 1940. They were most famous for giving the Soviet Union atomic secrets, specifically the design for the plutonium bomb dropped on Nagasaki. The spy ring Julius operated was also responsible for giving the Soviets proximity fuses and radar tubes, two technologies key to effective air defenses which would have played a large part if the Cold War had ever turned hot. 2. Noshir Gowadia gave B-2 Stealth technology to China. Noshir Gowadia is an Indian-American who was an engineer on early stages of the B-2 Spirit stealth bomber. Though Gowadia was paid $45,000 for his work, he was angry that he wasn’t kept on the project for future phases that were worth much more money. Gowadia wrote to a relative about his dissatisfaction and started his own consulting company. 3. Chi Mak’s betrayal put modern sailors in jeopardy. When the FBI raided Mak’s home, first in secret and later after arresting Mak and his wife, they foundstacks and stacks of classified information relating to naval technology, much of it still going into new Navy ships. The exact nature of what was released has not been made public since the technologies are still classified. 4. Ana Montes deliberately misled the joint chiefs while leaking secrets to Cuba. From 1984 to 2001, Ana Montes was slipping classified information to Cuba. Hers was a case of spycraft straight out of a novel. She’d don disguises to slip into Cuba, listen in South Florida to shortwave radio broadcasts from Cuba, and slip packages to handlers. 5. Robert Hanssen and Aldrich Ames dimed out every American spy they could name. Robert Hanssen and Aldrich Ames were two of the most damaging spies in U.S. history. Ames only operated from 1985 to 1993, while Hanssen spied from 1979 to 2001. Together, their leaks resulted in the exposure of hundreds of U.S. assets in the Soviet Union, but their most direct damage to the U.S. military was from exposing one high-level asset. Gen. Dmitri Polyakov was the head of Soviet intelligence and a major spy for the U.S., providing information on Soviet anti-armored missile technology, the Cuban Missile Crisis, and China. 6. John Anthony Walker told the Russians where all the U.S. subs were during the Cold War. For 18 years, Walker would leak the locations and encryption codes for U.S. assets as well as operational plans and other documents. He even recruited his son into the operation and tried to recruit his daughter who served in the Army, but she was pregnant and separating from the service. There are even claims that the sinking of the nuclear armed USS Scorpion was due to Walker’s espionage. 7. Larry Chin may have made the Korean War go on much longer. Larry Wu-Tai Chin was a translator for the U.S. Army during World War II. After the war, he became a translator for the CIA until his arrest in 1985. During this time, Chin passed many documents and photographs along to his Chinese handlers. 8. James Nicholson sold the intelligence team roster to Moscow. Harold James Nicholson’s espionage weakened U.S. observation of the Russian Federation during the mid-’90s. Nicholson was the head of CIA officer training program for two years, and he is believed to have sold the identities of all new officers trained during his tenure. In addition, he sold the assignment information for new officers headed on their first assignment. 9. James Hall III sold top-secret signal programs to the Soviets. U.S. Army signal intelligence warrant officer James Hall was assigned to a crucial listening post in West Berlin from 1982 to 1985. While he was there, he was feeding information on key programs to his Soviet handlers. Hall released tons of documents, intercepts, and encryption codes, exposing many operations to Soviet eyes. Arguably his most damaging action was letting the Soviets know about Project Trojan. Trojan would have allowed, in the case of war, the U.S. and its allies to target Russian armored vehicles, missiles, and planes by tracking their communication signals. Since Russia had the clear advantage in armored warfare at this point, the success or failure of Trojan could have decided who won the start of a war. 10. Col. George Trofimoff gave it all to the KGB through his brother the archbishop. The worst of the damage was done while Trofimoff was the chief of the U.S. Army’s operations at a NATO safe house where Soviet defectors were debriefed. The safe house had copies of nearly all U.S. intelligence estimates on Soviet military strength. Most weekends, Trofimoff would takes bags of documents home from the safe house, photograph them, and return them to the office before giving the photos to his brother, a Russian Orthodox priest who would go on to become the Archbishop of Vienna. 11. Benedict Arnold tried to abort America. Arnold handed over the plans to West Point and agreed to surrender the defenses in exchange for 20,000 British pounds (approximately $3 million today).