While serving as a vice-consul in Seoul, he was captured by North Korean forces in 1950. During his three-year imprisonment, he read Marxist texts and witnessed the heavy civilian toll of American bombings, deciding to switch sides and volunteer his services to Soviet intelligence (KGB). In the mid-1950s, the U.S. CIA and British MI6 launched Operation Gold (Operation Stopwatch), a secret mission to dig a 1,476-foot tunnel from West Berlin under the border into East Berlin to tap Soviet underground telephone and teletype cables.
George Blake learned of the plans in 1953—before construction even started and leaked the details directly to his KGB handlers. Rather than shutting the tunnel down immediately and risking Blake’s exposure, the KGB allowed the Western intelligence agencies to dig the tunnel and feed them monitored information for nearly a year before “discovering” it in April 1956 for a propaganda advantage. Blake was eventually exposed in 1961, sentenced to 42 years in a British prison, and later escaped to the Soviet Union in 1966, where he lived until his death at age 98.
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American intelligence spent more than a year building a secret tunnel beneath Berlin without knowing the Soviets had already discovered the plan. In the spring of 1955, the CIA and Britain’s MI6 began intercepting telephone and telegraph communications through an underground tunnel extending 1,476 feet toward Soviet-controlled East Berlin. The operation was supposed to give Western intelligence unprecedented access to Soviet military secrets. But a Soviet agent inside British intelligence had revealed the project before construction began. The KGB chose to let the Americans complete their tunnel.
The operation grew from a major problem facing Western intelligence in the early Cold War. Soviet military communications across Eastern Europe were increasingly transmitted through underground telephone and telegraph cables rather than easily intercepted radio signals. Berlin, divided between Western and Soviet occupation sectors, contained important communication routes linking Soviet forces in East Germany with commanders elsewhere. American intelligence officers believed that reaching those cables could reveal troop movements, military organization and political intentions. The challenge was doing so without alerting Soviet or East German security forces.
In January 1954, CIA director Allen Dulles approved the project, later known as Operation Gold. A seemingly ordinary facility in West Berlin provided cover for the extraordinary construction work. Engineers created a warehouse and supporting buildings while secretly excavating beneath the divided city. The project eventually required the removal of approximately 3,100 tons of soil, along with 125 tons of steel lining and enormous quantities of construction material. The excavated earth had to be concealed within the compound rather than visibly transported away. British technicians subsequently installed equipment to tap the cables carrying Soviet communications.
The first intelligence collection began in May 1955. American and British analysts received an enormous stream of conversations and messages that had previously been beyond their reach. The operation produced approximately 50,000 reels of recording tape, including tens of thousands of hours of telephone calls and a vast volume of telegraph traffic. Analysts extracted information about Soviet forces, military activities and conditions within the Eastern bloc. From the Western perspective, the tunnel was a technical success. What the operators did not know was that their enemies had possessed advance warning from someone working inside MI6.