For all the high-profile successes soviet espionage had – obtaining details on the Manhattan Project as well as updates on America’s progress with it, penetrating the entire Treasury Department, installing an eavesdropping device in the American embassy in Moscow that went undetected for years – they did still suffer their share of setbacks. In the U.S., the most known case is of the husband-and-wife spy duo of Julius and Ethel Rosenberg, but another case, less well known, is of engineer Vladimir Vetrov.

On this day, July 19, 1981, France’s Prime Minister François Mitterrand shared with President Ronald Reagan a report from the Direction de la Surveillance du Territoire (the French CIA.) A Soviet defector, Vetrov, codenamed “Farewell,” had come forward to them with information on a Soviet spy ring operating in both U.S. and Europe. It was information immensely helpful for the U.S. in maintaining their technical advantage.

Vetrov was in charge of overseeing the spy efforts of “Line X,” the network of spies capturing and the secrets of Western technology. He had become increasingly disillusioned with the communist system and began cooperation with the French to pass along secret Soviet documents and reveal the entire structure of the 250-man Line X. Some of the spies were arrested, others deported, and some were kept in their position but fed faulty information to relay to the Soviet government.