Operation Gold

Operation Gold was a joint operation conducted by the American Central Intelligence Agency and the British MI6 Secret Intelligence Service in the 1950s to tap into landline communication of the Soviet Army headquarters in Berlin using a tunnel into the Soviet-occupied zone. This was a much more complex variation of the earlier Operation Silver project in Vienna.

The plan was activated in 1954 because of fears that the Soviets might be launching a nuclear attack at any time, having already detonated a hydrogen bomb in August 1953 as part of the Soviet atomic bomb project. Construction of the tunnel began in September 1954 and was completed in eight months.