On a hot afternoon on the 20th of May 1978, special agents from the Federal Bureau of Investigation (FBI) based in New York arrested three Soviets near a major crossroad in New Jersey after catching the gentlemen picking up classified documents.

An arrest that involved months of meticulous planning, over a year of cautious surveillance, and hiring the perfect double agent to get the job done, Operation Lemonade has been one of the most successful and significant FBI operations to uncover the Soviet Union’s infamous Komitet Gosudarstvennoy Bezopasnosti (KGB) spies that have been infesting the US soil since the onset of the Cold War.

Straight out from the intelligence agency’s archive files, here’s how a US Navy lieutenant duped the Soviets and helped apprehend the first-ever KGB spies tried for espionage in America.

Navy Officer Turned Double Agent

The FBI has long been closely monitoring suspicious activities inside the Soviet Union’s United Nations headquarters for espionage. Yet, without concrete evidence, the intelligence agency is unable to intervene.