Following the end of World War II and the defeat of Germany, the world prepared for a new and different phase of conflict known as the Cold War. Old alliances faded away, replaced by new ones between two camps: one Eastern and the other Western. This transition came after the Soviet Union, now Russia, developed its atomic bomb, and with the involvement of the United States, North Korea, and China in a bloody quagmire on the Korean Peninsula. Additionally, there were numerous conflicts and espionage activities across Europe, particularly centered in the divided city of Berlin. Each side attempted to assert its influence over the city. In 1954, the CIA launched a highly risky operation codenamed “Operation Gold,” a bold plan to exploit communication lines extending from Western France to the heart of the Soviet Union and Eastern Europe during the early Cold War.
The origins of “Operation Gold” date back to 1948 in Vienna, Austria, which, like Berlin, was a hotbed of espionage in the immediate post-war years. Vienna was divided into four military zones managed by Britain, the United States, France, and the Soviet Union. The British, keen to learn as much as possible about Soviet communications in Vienna, sent one of their top agents, Peter Lunn, to investigate. Lunn discovered that the Soviets were using Austrian landlines to connect their military headquarters in Vienna with Moscow. He also found that all communications from Moscow to its military center in Austria were routed through the Imperial Hotel. Consequently, British intelligence (MI6) purchased a building near the site and dug a tunnel over 20 meters long from the basement to access the main communication cables in an operation dubbed “Operation Silver.” To avoid drawing unwanted Soviet attention, MI6 established a front company in the building, which successfully disguised their true intentions. This allowed British spies to carry out their covert work undetected. During a meeting with U.S. intelligence officials, the British shared their success, and the two sides collaborated, exchanging valuable information. The British were able to learn Soviet strategies and stay updated on their actions and developments. The success of “Operation Silver,” which ran from 1948 to 1952, served as a model for the CIA’s subsequent ambitious project, “Operation Gold.”
Returning to Berlin, after its division, the United States moved its military headquarters to the bombed city in July 1945. The American sector was adjacent to the Soviet-controlled area in Berlin’s sprawling “Zehlendorf” district. CIA activities in Berlin were covertly codenamed “BOB.” Two of the CIA’s most important teams, the covert intelligence branch and counterintelligence, were tasked with countering Soviet activities in Berlin. The Soviets had a tight grip on their sector and focused on gathering extensive intelligence on Americans, including informants, agents, and important figures in the city. This required American intelligence operatives to conduct extensive work, not only focusing on military intelligence but also on the economic activities within the vast Soviet-controlled sectors of the city, utilizing their own agents who managed to infiltrate the Soviet intelligence headquarters in Berlin, located in the Karlshorst district. They tracked the development of the Soviet atomic bomb in the late 1940s, with significant support from the American military, which played a major role in “BOB” by providing logistical support. Over time, “BOB” became the largest intelligence gathering agency in Europe, playing a crucial role in keeping Washington informed during the Berlin Blockade of 1948. Its success allowed it to offer its expertise when “Operation Gold” was initiated.
Building on the success of the Vienna operation, CIA leadership studied how to replicate the British achievement, this time under the noses of the Soviets and their East German allies in Berlin. After extensive research by the agency’s top minds, it was decided that the best approach was to focus on underground cables buried beneath the city. The Americans realized that monitoring cables from above ground was not feasible, but if listening devices were placed underground, the chances of detection would be minimal. To validate this, a CIA double agent in 1953 placed a listening device on a cable in East Berlin, linking it to local phone lines in West Berlin. This test proved highly successful and undetected, leading the CIA to proceed with “Operation Gold.”
Throughout 1953, a comprehensive scientific effort was dedicated to all aspects of the plan, testing every possible scenario. When the plan was finalized, its broad outlines were sent to then-CIA Director Allen Dulles for final approval. Dulles was impressed and deemed the plan worthy of pursuit, giving it the green light to become the largest secret operation of the Cold War. After careful consideration by “BOB” agents, the decision was made to start digging in the “Tegel” area of Berlin. Work officially began in February 1954, using a radar site for cover. Despite constant Soviet surveillance of American intelligence activities in Berlin, the Soviets did not notice when Americans began constructing a building at the site, mistakenly believing it to be another military facility.
During the planning of this operation, the CIA decided to brief the British on “Operation Gold.” One of the British intelligence officers present was George Blake, a Soviet spy who took detailed notes on the briefing and immediately reported the information to his Soviet contact, Sergei Kondrashev, who in turn informed his superiors. The Soviet leaders convened a meeting to discuss the issue.
The Americans selected a capable officer, William King Harvey, to manage “Operation Gold.” Harvey had previously worked for the FBI but left after a dispute with Director J. Edgar Hoover to join the CIA’s counterintelligence division. One of his early assignments was to uncover Soviet spy Kim Philby, who worked for British intelligence in Washington, D.C., in 1952. Harvey was assigned a sensitive role as head of the CIA station in Berlin. Given that it was practically impossible for “BOB” agents to infiltrate East Germany, Harvey secretly recruited several double agents working for the East Germans, particularly those involved in communications, and gathered important information on East German government communications setup. One of the key double agents in “Operation Gold” was a source codenamed “The Sniper,” who provided “BOB” with insights into Soviet penetration of Western interests in Berlin. Harvey revealed some details of “Operation Gold” to a few men in “BOB,” withholding information about the tunnel even from Robert Murphy, the second-in-command of “BOB” in 1954. Murphy was only briefed by Allen Dulles about the progress and given the green light for full-scale implementation after secret meetings with British intelligence in London.
The U.S. Army Corps of Engineers began digging the tunnel under East Berlin, using the same tunnel dimensions as tested in the New Mexico desert. The excavation was conducted covertly to avoid detection by West German authorities, who were misled about the nature of the work. Harvey deceived the West Berlin mayor, claiming that American engineers were only conducting geological work to prevent potential Soviet sabotage of Berlin’s sewer system. The tunnel construction was complex, extending over a considerable distance beneath sandy soil to reach the cable area near a busy highway used by East German and Soviet troops. American workers reached it on August 28, 1954. However, the following month, they encountered an obstacle when water seeped into the excavation, requiring pumps to address the problem. The tunnel was completed and fully equipped by February 28, 1955, stretching 460 meters directly under Soviet territory, leading to the Soviet main cable facility. The tunnel consisted of interconnected sections, with three pre-fabricated rooms to house personnel monitoring the site underground, and air conditioning systems for minimal comfort. Each room had a metal door separating it from the rest of the tunnel. The first spying equipment was installed in May 1955, and the task of accessing the cables and eavesdropping on Soviet lines continued until August of the same year.
“Operation Gold” proved successful, allowing American listeners to monitor over 500 calls simultaneously. By the end of the operation, the CIA had recorded conversations on approximately 50,000 reels of tape, intercepted 443,000 written conversations between the Soviets and East Germans, and collected 40,000 hours of phone conversations, along with 1,750 intelligence reports. The tunnel represented a vast intelligence treasure for the West, capturing every significant political and military conversation from East Germany to Soviet regions across Europe. Despite the sophisticated technology used in the tunnel, unexpected weather conditions led to its downfall. In April 1956, heavy rainfall flooded Berlin, exposing one of the tunnel’s chambers to Soviet maintenance crews, forcing CIA operatives to flee quickly. According to reports, Harvey left behind a sardonic note for the Soviets, stating, “You are now entering the American sector.”
When news of “Operation Gold” was finally revealed, the reaction in the United States was jubilant, with the press giving it prominent headlines nationwide. The New York Times described the operation as a daring adventure worthy of thriller material, while the New York Herald Tribune hailed it as an example of the CIA’s ability to undertake bold missions. “Operation Gold” was indeed the first major covert project undertaken by the CIA during the Cold War, earning William Harvey the Distinguished Intelligence Medal at a secret ceremony held by the agency’s director. Subsequent investigations revealed that British double agent George Blake had alerted the Soviets about the American plans. Soviet leaders faced the choice of either halting a potentially damaging operation or losing a valuable agent. The decision was made to protect their source and let the Americans build the tunnel without interference. When Soviet maintenance crews “accidentally” discovered the tunnel, there was no option but to terminate the operation. Blake was later arrested and confessed to leaking information about the tunnel to the Soviets, receiving a 42-year prison sentence. He boldly escaped from his high-security prison in England in 1966 and made his way to Moscow, where he was treated as a hero.
Years passed, and the tunnel remained, but in the 1990s, a 12-meter section was moved to the Allied Museum, and other parts were displayed at the CIA Museum.
