June 14, 2000 U.S. Army Colonel George Trofimoff of Florida becomes the highest ranking U.S. military officer charged with spying. The FBI says Trofimoff was a spy for 25 years, photographing U.S. documents and passing the film to KGB agents.

Nov. 29, 1999 U.S. military officials charge Navy code breaker Daniel King with selling data to Moscow .

October 1998 A retired U.S. army intelligence analyst named David Sheldon Boone is charged with selling secrets to Moscow after FBI sting.

December 1996 FBI arrests one of its own, agent Earl Pitts. Pitts, who was stationed at the FBI Academy in Quantico , Va. , had been selling secrets to Russia for nine years. He was paid more than $224,000. Pitts was caught in a sting, giving FBI cipher codes and his own security badge to FBI undercover agents he thought were his new Russian handlers. He was sentenced to 27 years.

November 1996 The FBI arrests veteran CIA officer Harold Nicholson on charges of spying for Russia . Nicholson was at a Washington airport on his way to Europe to meet with his Russian intelligence handlers. At the time of his arrest, he was carrying rolls of exposed film that contained secret information. In March 1997, Nicholson pleaded guilty to the charges and was sentenced to 23 years.

February 1994 Aldrich Ames, 52, an alcoholic who had been a CIA employee for more than 31 years is charged, along with his wife, with spying for the Soviet Union and then later for Russia. Ames passed information to the KGB from 1985 to 1994 including the identities of U.S. agents and U.S. counterintelligence techniques. It was called the most damaging espionage case in American history. Later CIA chief John Deutch told Congress Ames compromised more than 100 U.S. spies. Ten were executed and others turned by the KGB to then feed selective information to the CIA. Ames and his wife received over $2.7 million, the most money paid by the Soviet Union/Russia to an American spy. Ames pleaded guilty in 1994 and was sentenced to life.

1986 Ronald W. Pelton, a former employee of the U. S. National Security Agency, is convicted of selling top-secret signals intelligence information to the Soviet Union . Pelton revealed to his handlers that U.S. intelligence had tapped Soviet undersea cables and was listening to navy communications.

1985 What the media call the Walker Family spy ring is exposed. A retired U.S. Navy Warrant Officer, John A. Walker Jr. pleaded guilty along with his son, Navy Seaman Michael L. Walker, 22, to charges of spying for the Soviet Union . John Walker passed secrets to the Soviets while he was a shipboard communications officer. After he retired, he recruited his son, brother and a friend. Walker 's brother, Arthur Walker, a retired Navy lieutenant commander, was convicted of stealing secret documents from a defence contractor. Jerry Whitworth, a Navy chief petty officer, was convicted in 1986 of passing secret Navy codes to Walker .

1985 Former CIA officer Edward Lee Howard flees from the U.S while the FBI is investigating him for spying. Howard was suspected of disclosing the identities of CIA agents in Moscow . He turned up in the Soviet Union in 1986.

1980 Former CIA agent David H. Barnett pleads guilty to spying for the Soviet Union between 1976 and 1979 while based in Indonesia . Barnett was the first current or former CIA agent convicted of espionage. He exposed the identities of 30 U.S. agents.

May, 1957 KGB Lieutenant Colonel Reino Hayhanen defects to the United States in Paris and names members of a Soviet spy ring operating in the U.S. Hayhanen had been a spy in the U.S. since 1954, reporting to spy masters named "Mikhail" and "Mark". Mikhail Nikolaevich Svirin was a Soviet diplomat at the UN. Mark was using a cover name of Emil R. Goldfus. He ran a small photography studio in New York . In reality, "Mark" was KGB Colonel Rudolf Ivanovich Abel, who had been spying in the U.S. since 1948. On October 25, 1957 , Abel was convicted of spying and sentenced to 30 years in jail. On February 10, 1962 , he was exchanged for the American U-2 spy-plane pilot, Francis Gary Powers, who was held by the Soviets. An American member of the ring, code named " Quebec ," was an Army sergeant named Roy Rhodes, who was court-martialed and sentenced to five years.

1949 The FBI receives a tip that the Soviets had stolen the secrets of the American atom bomb. As a result of the preliminary investigation, the British arrest Emil Julius Klaus Fuchs, a German-born atomic scientist. Fuchs admits his involvement in Soviet atomic espionage. The FBI identifies Fuch's contact as Harry Gold, a Philadelphia chemist. That leads to David Greenglass, a U.S. Army enlisted man who was stationed at the U.S. atom bomb lab at Los Alamos , New Mexico , in 1944 and 1945. Gold's handler was Anatoli Yakovlev, a former Soviet vice-consul in New York City . FBI interrogation of Greenglass and his wife brings the arrest of Julius and Ethel Rosenberg. Ethel is Greenglass's sister. Then two other spies, Max Elitcher, a naval ordnance engineer and Morton Sobell, a radar engineer and former classmate of Julius Rosenberg, are arrested as part of the spy network.

David Greenglass pleaded guilty and testified against his colleagues. Gold also testified in the case.

On March 29, 1951 , Julius and Ethel Rosenberg, and Morton Sobell were found guilty. The Rosenbergs were sentenced to death and Sobell to 30 years. The Rosenbergs were executed at Sing Sing Prison, New York on June 19, 1953 . David Greenglass received a 15-year sentence.

1948 William Weisband, a Russian-speaking member of the U.S. Armed Forces Security Agency (the predecessor of the NSA) betrays U.S. codes to the Soviet Union . The Soviets change their codes and this hampers U.S. actions in the early days of the Korean War. Weisband had been a Russian spy since 1934, but he was never charged with espionage. He was fired from the NSA and served a year for contempt of a grand jury. His actions were not revealed until the 1990s

1940 - Fuchs sent to internment camp in Canada as and Enemy Alien.

1935 - Harry Gold (American chemist) begins espionage for USSR .

1933 - Klaus Fuchs emigrates to England from Germany , where he was already a Communist.