Venona Cables Are Declassified

Venona was the code name used for an American project for decrypting Soviet diplomatic messages sent between the Soviet consulate in the United States and Moscow. The decrypted messages identified numerous Soviet spies and provided insight into the workings of Soviet espionage in the United States. The release of these decryptions in the mid-1990’s revised historians’ understanding of the early years of the Cold War.

Summary of Event

In July, 1995, the National Security Agency (NSA) began to release transcripts of Soviet consular messages that had been intercepted and decoded during the Cold War. This top secret decryption effort was code-named Venona, a randomly assigned word with no meaning. In addition to exposing the methods of Soviet spy craft throughout the 1930’s-1950’s, the Venona transcripts helped to confirm the identities of numerous Cold War spies whose complicity with the Soviets had been debated by many historians in the 1970’s and 1980’s. Among the most prominent of these were Alger Hiss and Julius and Ethel Rosenberg. Cold War;Venona project
Venona project
U.S.-Soviet relations[U.S. Soviet relations]
Espionage, Cold War
[kw]Venona Cables Are Declassified (July, 1995)
[kw]Declassified, Venona Cables Are (July, 1995)
Cold War;Venona project
Venona project
U.S.-Soviet relations[U.S. Soviet relations]
Espionage, Cold War
[g]North America;July, 1995: Venona Cables Are Declassified[09270]
[g]United States;July, 1995: Venona Cables Are Declassified[09270]
[c]Cold War;July, 1995: Venona Cables Are Declassified[09270]
[c]Diplomacy and international relations;July, 1995: Venona Cables Are Declassified[09270]
Gardner, Meredith
Lamphere, Robert
Fitin, Pavel
Rosenberg, Julius
Rosenberg, Ethel
Hiss, Alger

The Venona project began in 1943. The head of the U.S. Army’s Signal Intelligence Service (SIS), fearing secret German and Soviet peace negotiations, ordered that intercepted Soviet consular messages be decrypted to validate this expectation. These telegraph and radio messages between the Soviet ambassadorial staffs in the United States and their superiors in Moscow were encrypted using a “one-time pad system.” This method replaces words and letters with numeric sequences from a page filled with random number sequences; both sender and receiver have identical copies of this page, and, after one use, the page is destroyed. The strength of this system is that every message’s code would differ from that on the next page, so it is nearly “unbreakable.” To facilitate several messages, books of these one-time pads were printed in Moscow and sent to the embassies in diplomatic pouches that by treaty could not be opened or inspected by the host countries. All nations’ ambassadors communicate by coded transmissions, but Soviet use of the one-time pad system made their communications seem very secure.

Unfortunately for Russia, the first few months after the German invasion in 1941 resulted in confusion as the Germans advanced on Moscow. It appears that during this chaotic period, the Soviets reprinted and issued a number of duplicate one-time pads so that during the war a number of the sequences were repeated, thus making the code vulnerable. America’s first efforts to crack these codes failed, but in 1943 the SIS began to recognize that some sequences were being reused. After much work, some messages could be partially decoded. This discovery was made in the SIS facility at the Arlington Hall Station, so throughout World War II Venona efforts were ascribed to Arlington Hall. In 1946, Meredith Gardner was assigned to Venona. A skilled linguist and veteran of the successful breaking of Japan’s diplomatic codes, Gardner became a key player in the project.

Meredith Gardner (left) works as a code breaker for the Venona project.

(U.S. Department of Energy)

Deciphering the numeric codes was made more difficult by the Soviets’ use of cover names. Every person mentioned—whether target or agent—was to be referenced with a cover name (for example, President Franklin D. Roosevelt was “KAPITAN”). To make sense of intercepted cables, Gardner first had to break the codes so that letters could be discerned, combine the letters into probable words, and then link the cover names to individuals. In December, 1947, Gardner transcribed a cable that listed the cover names of Soviet agents who were supplying information on America’s atomic weapons program. After this, it was decided to combine the SIS efforts with the expertise of the Federal Bureau of Investigation Federal Bureau of Investigation;Venona cables (FBI), and for the first time since the 1920’s, when the FBI began investigating Russian spies, it had access to secret Soviet instructions. Prior FBI efforts had been based on surveillance, wiretaps, and the confessions of a small number of Soviet spies who had defected for reasons of fear or greed.

In 1947, the FBI assigned Robert Lamphere to Venona as the agency’s chief agent. By linking the insights offered by confessions with his knowledge of Soviet operations, Lamphere was able to help Gardner by giving context to the decoded messages and thus identify cover names. Further assistance was provided by British code breakers in Cheltenham, England, at the Government Communications Headquarters (GCHQ), who had been trying to crack Soviet codes on their own. This assistance proved significant, as did that of Canadian officers who debriefed a defected Soviet cipher clerk in 1945.

These combined efforts were aided by the Soviets’ centralized operational style of strict control over subordinates. Foreign espionage was controlled by the first directorate of the KGB (the best-known name of the Committee for State Security, the Soviet Union’s apparatus for collecting foreign and internal intelligence). Each embassy’s intelligence officers sent frequent reports to the KGB and in return received detailed instructions. During World War II, the commander of the first directorate was Lieutenant General Pavel Fitin, code-named VIKTOR. Under Fitin, Soviet intelligence officers recruited Americans to spy on government programs, industrial developments, and weapons developments. A great number of these spies were recruited from members of the Communist Party of the United States. Venona decryptions, when added to Lamphere’s understanding of the Soviet organization, were pivotal in the identification of several Soviet operatives.

This effort was time-consuming, as each successful decryption provided clues that were used to break earlier unread cables. Venona operations continued into 1980, although the bulk of the cables were broken between 1947 and 1952. Ultimately, only a small portion of the several thousand intercepted cables were ever broken—less than 3,000—and those were messages sent between 1942 and 1945, with a few sent as late as 1948. It appears that the duplicate one-time pads were used up during the war and replacement pads were not breakable by the Venona staff.

Regardless, Venona proved very useful. Decrypts corroborated the claims of the Soviet defectors such as Whittaker Chambers who had described Soviet methods, successes, and agents. The link between their confessions and decrypts provided nearly certain identification of some agents. For example, the identification of Julius Rosenberg as a spy in the atomic bomb project was immeasurably strengthened by decrypt number 1657 of November 27, 1944. Similarly, the Soviet agent ALES was identified by Lamphere as Alger Hiss based on details found in Venona transcripts. The reports to Moscow also indicated that Soviet agents were operating in the Department of the Treasury, the Office of Strategic Services, the War Department, the Department of State, and the Justice Department.


The release of the Venona cables is an important part of ongoing efforts to understand the Cold War. In the aftermath of the Vietnam War and the Watergate scandal, many historians claimed that government prosecutions of American spies were based on hysteria, shoddy FBI procedures, and perhaps perjured testimony. The trial of the Rosenbergs, for example, relied on evidence given by Ethel Rosenberg’s brother, David Greenglass, who had been a courier for a Soviet espionage ring. Although some of his testimony can be described as perjured, the decision was made to use it rather than expose the Venona project to public view. The revisionist writings of the 1970’s have been compromised by the Venona releases and the opening of some KGB archives in the first years after the fall of the Soviet government. The result is a more nuanced and thorough understanding of the espionage conflict between the United States and the Soviet Union.

While Venona certainly provided evidence of Soviet spies in many agencies of the U.S. government, this evidence was fragmentary and tentative until the mid-1990’s, when some Soviet archives were opened to historians. While these two sources certainly make it clear that many Americans did spy for Moscow, their impact is easily overstated. For example, the U.S. atomic bomb effort, the Manhattan Project, was a huge undertaking. Perhaps 100,000 people worked on it—most unknowingly. The Soviet spies identified by Venona number perhaps a few dozen, and only one was placed significantly. Thus, although Venona confirmed the presence of Americans operating as spies for the Soviets, it did not prove that their efforts greatly compromised U.S. security.

The 1995 release of the Venona decoded top secret transcripts of Soviet consular messages helped to rewrite the history of the Cold War. Venona provided the United States with insight into the personnel and methods of operations of Soviet espionage throughout the 1930’s-1950’s and helped confirm the identities of numerous individuals accused of spying for the Soviets. Among the most prominent of these were Alger Hiss and Julius and Ethel Rosenberg. Cold War;Venona project
Venona project
U.S.-Soviet relations[U.S. Soviet relations]
Espionage, Cold War

Further Reading

  • Benson, Robert Louis, and Michael Warner. Venona: Soviet Espionage and the American Response, 1939-1957. Washington, D.C.: National Security Agency, 1996. The official description and analysis of the project. Provides 450 pages of transcripts of reports and analyzed cables.
  • Romerstein, Herbert, and Eric Breindel. The Venona Secrets: Exposing Soviet Espionage and America’s Traitors. Washington, D.C.: Regnery, 2000. Written by two former American intelligence agents, the book, however biased, provides an in-depth description of the many Soviet activities exposed and confirmed by Venona.
  • West, Nigel. Venona: The Greatest Secret of the Cold War. London: HarperCollins, 1999. Focuses primarily on British efforts, but provides a well-balanced and insightful description of the Venona operations.

Détente with the Soviet Union

Dissolution of the Soviet Union