Berlin Tunnel Ceases Operations

Photo By Lori Stewart | Interior view of the underground tunnel. (Central Intelligence Agency)  

UNITED STATES

04.17.2023

Story by Lori Stewart 

U.S. Army Intelligence Center of Excellence

by Lori S. Stewart, USAICoE Command Historian

22 APRIL 1956
On 22 April 1956, East German workers attempting to fix interruptions in Soviet tele-communications discovered tapping equipment on Soviet lines in East Berlin. The United States and British intelligence had placed the tap via an underground tunnel in 1955 to intercept Soviet military communications. Although the Central Intelligence Agency (CIA) and British MI-6 managed the “Berlin Tunnel” project, U.S. Army intelligence personnel played a role in its short period of operation.

After World War II, the Soviets shifted from wireless communications to encrypted landlines for most military traffic. To intercept their telephone and telegraph messages, the CIA and British MI-6 initiated the Berlin Tunnel project. Codenamed Operation GOLD by the CIA, the project required construction of a 1,476-foot-long, 78-inch-diameter, underground tunnel between the American and Soviet sectors of Berlin to access the main Soviet communication cables. Construction of the tunnel began in 1954 and interception operations started 11 May 1955. Hour after hour, six hundred tape recorders captured all Soviet communication signals on the lines onto thousands of reels of magnetic tape.

The beginning of the tunnel was located in Rudow near the border between the two sectors. A large structure, purported to be a Quartermaster warehouse, concealed the tunnel opening, while the building’s various antennae appeared to be related to nearby airport operations. In fact, the antennae were for electronic intelligence (ELINT) operations conducted by the Signal Corps’ 9539th Technical Service Unit. Shortly after the operation commenced, the Army Security Agency (ASA) assumed responsibility for all ELINT operations, and the 9539th was integrated into ASA as the 22d ASA Detachment, 7222d Defense Unit.

In addition to conducting ELINT operations, the 22d ASA Detachment had a five-person processing unit monitoring and scanning the more productive circuits for “hot” intelligence. One of these men was 22-year-old Cpl. Eugene Kregg (who later changed his last name to Kovalenko). Recruited by the CIA out of the Russian course at the Army Language School, Kregg was the only Army linguist working on the intercepts; the others were CIA or British intelligence, although one was from the U.S. Navy. Corporal Kregg recalled spending “virtually all my time listening to freshly recorded tapes, which contained material that couldn’t wait to be analyzed elsewhere…sixteen hours a day, seven days a week.”

While Kregg labored on “hot” intercepts in Berlin, other analysts worked on less time-sensitive telegraphic intercepts in the Tape Processing Unit (TPU) in Washington, D.C. or on voice intercept materials at a joint center in London. Tapes were ferried by air to these two processing centers on a weekly basis. While most of the analysts in Washington and London were civilians, the CIA also recruited from the Army Language School the only six Army personnel assigned to the TPU. They were Russian linguists William O’Connell, William Simpson, and Robert Browne and German linguists Robert Quinn, Donald Andrews, and Walter Huth.

When the Germans discovered the tap on 22 April 1956, the Berlin Tunnel’s operations ceased. In reality, a mole in British intelligence had already alerted the Soviets to the wiretapping. Believing their communications to be secure, the Soviets had allowed the operations to continue to protect their source. Operation GOLD yielded nearly 50,000 six-hour reels of recorded plain text and enciphered traffic, of which nearly 30,000 were fully transcribed. Belying the Soviets’ confidence in their telecommunications security, the information obtained contributed significantly to American and British understanding of Soviet and East German Army order of battle, including details on unit reorganizations, training plans, and the development of new capabilities.

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• Date Taken: 04.17.2023
• Date Posted: 04.17.2023 10:57
• Story ID: 442731
• Location: US