After the war Weisband was assigned to help decode a backlog of communications between Moscow and its foreign missions. By 1945, over 200,000 messages had been transcribed and now a team of cryptanalysts attempted to decrypt them. The project, named Venona (a word which appropriately, has no meaning), was based at Arlington Hall, Virginia. (2) Soviet messages were produced in exactly the same way as Japanese super-enciphered codes. However, "where the Japanese gave the codebreakers a way in by repeatedly using the same sequences of additive, the Russian system did not. As its name suggests, the additive appeared on separate sheets of a pad. Once a stream of additive had been used, that sheet was torn off and destroyed, making the message impossible to break." (3)

Weisband worked very closely with Meredith Gardner, the head of the project. It was not until 1949 that Gardner made his big breakthrough. He was able to decipher enough of a Soviet message to identify it as the text of a 1945 telegram from Winston Churchill to Harry S. Truman. Checking the message against a complete copy of the telegram provided by the British Embassy, the cryptanalysts confirmed beyond doubt that during the war the Soviets had a spy who had access to secret communication between the president of the United States and the prime minister of Britain.

The Armed Forces Security Agency requested copies of all transmissions handled by the British Embassy and began matching them against the encoded messages in the New York-to-Moscow channel, working backward through the code book and arriving at the additive. Gradually they were able to transcribe these messages. It now became clear that there had been a massive hemorrhaging of secrets from both the British Embassy in Washington and the atomic bomb project at Los Alamos, New Mexico.

William Weisband immediately notified the NKVD that the Venona Project was on the verge of success. To make sure that the FBI was unaware that they knew that the code was about to be broken, they continued to use it. The "operatives" were instructed "every week to compose summary reports or information on the basis of press and personal connections to be transferred to the Center by telegraph." As Allen Weinstein, the author of The Hunted Wood: Soviet Espionage in America (1999) has pointed out the "Soviet intelligence's once-flourishing American networks, in short, had been transformed almost overnight into a virtual clipping service." (4)

In February 1948 a Soviet official wrote an internal memorandum about the work of Weisband. "For one year, a large amount of very valuable documentary material concerning the work of Americans on deciphering Soviet ciphers, intercepting and analyzing open radio-correspondence of Soviet institutions (the Venona project), was received from (Weisband). From these materials, we came to know that, as a result of this work, American intelligence managed to acquire important data concerning the stationing of the USSR's armed forces, the productive capacity of various branches of industry, and work in the field of atomic energy in the USSR... On the basis of Weisband's materials, our state security organs carried out a number of defensive measures, resulting in the reduced efficiency of the American deciphering service. This has led to the considerable current reduction in the amount of deciphering and analysis by the Americans." (5)

Weisband passed documents to Yuri Bruslov, his Soviet contact in the United States. In August 1948, Weisband became worried that he would be exposed as a spy and switched to dead-letter drops. Weisband also asked Bruslov to request asylum for him in the Soviet Union. He was too important a source and therefore they began paying him regular sums of $600 for his efforts. In 1949 Bruslov was replaced by Nikolai Statskevich. In December 1949, the FBI identified Statskevich as a Soviet agent. They also discovered that he was having regular meetings with Weisband.

The FBI was unwilling to arrest and charge Weisband because they knew that this would reveal details of the Venona Project. Instead, Weisband was ordered to appear before a grand jury hearing on the Communist Party of the United States. On 10th April 1950, Statskevich had his final meeting with Weisband and gave him $1,694 in cash to maintain his silence. In November 1950, Weisband, who had failed to appear before the grand jury, was convicted of contempt and sentenced to a year in prison. (6)

According to his son after leaving prison he worked as an insurance salesman. "My father had a very interesting job from my perspective when I was a child. He served as sort of a door-to-door insurance salesman, debit salesman, in Alexandria, Virginia. He had one of the largest debit books in the state. Most of our customers were African-American people, indigenous if you will. He would knock on doors. At some point in my father's life, as he got older, he had a hernia operation and ended up losing his leg." (7)

William Weisband died of a heart-attack on 14th May, 1967. Weisband was not exposed as a Soviet agent until much later. As David C. Martin, the author of Wilderness of Mirrors (2003) reported: "Despite Weisband's leak to the Soviets, the code break would remain a closely guarded secret for more than thirty years while cryptanalysts continued to cross-check the backlog of intercepted messages, eventually reconstructing most of the old Russian code book. Whatever marginal value the continued secrecy of the project might have had seemed more than outweighed by the public suspicion and distrust of the government's actions in the Hiss and Rosenberg cases." (8)

In January 2002, his son, William Weisband, Jr., gave an interview to PBS: "I'm proud, very, very proud of who I am and who my father was. It's like peeling an onion, every book I read and every new story that comes out. It's very revealing and very intriguing. That's activity that happened before I was born, from the 1930s to the 1950s. I was born sometime after that so my perception of my father - it's like reading about a historical figure that you just happen to be very closely related to.... I can only imagine that he believed that what he was doing was the right thing to do. As you know from studying some of these characters, this Cold War period, they're very principled people, very ideological, and very sincere about their beliefs. I can only imagine that he really believed what he was doing was right." (9)

(1) Allen Weinstein, The Hunted Wood: Soviet Espionage in America (1999) page 286 and 291

(2) David Stout, The New York Times (18th August, 2002)

(3) The Daily Telegraph (20th August, 2002)

(4) Allen Weinstein, The Hunted Wood: Soviet Espionage in America (1999) page 286

(5) Yuri Bruslov, memorandum on William Weisband (February, 1948)

(6) Allen Weinstein, The Hunted Wood: Soviet Espionage in America (1999) page 293

(7) William Weisband, Jr., interviewed by PBS (January 2002)

(8) David C. Martin, Wilderness of Mirrors (2003) page 43

(9) William Weisband, Jr., interviewed by PBS (January 2002)