Decoded Soviet Messages Affirm Rosenberg Spy Case : Espionage: Transcripts appear to settle debate over couple’s 1953 executions. Notes show atomic secrets passed.

Providing startling evidence on one of the most divisive controversies of the Cold War, intelligence officials revealed Tuesday that the U.S. investigation that led to the executions of Julius and Ethel Rosenberg in 1953 was based on intercepted Soviet messages that identified them as atomic spies.

The government declassified and released the transcripts of 49 messages intercepted from Soviet intelligence agencies dating from the 1940s, revealing that the FBI’s investigation of the Rosenbergs was prompted by top-secret--and damning--intelligence never mentioned in the trial of the Rosenbergs, the first U.S. civilians put to death for espionage.

The transcripts “may lay to rest one of the most significant controversies of the Cold War,” observed David Kahn, historian of the National Security Agency, which released the messages during a ceremony at the headquarters of the Central Intelligence Agency. “This shows that the Rosenbergs spied for the Soviet Union.”

“This is the stuff of spy novels,” added CIA Director John M. Deutch.

The messages were intercepted and analyzed as part of a top-secret code-breaking program called Venona, which was begun during World War II and which led the FBI to penetrate an extensive Soviet espionage ring aimed at stealing the secrets of the American atomic bomb. The messages were kept secret because the government did not want to compromise the Venona program.

Started by Army intelligence in 1943 and later run by the National Security Agency, Venona broke Soviet diplomatic and intelligence codes until the program was compromised by a Soviet agent--perhaps the infamous British traitor Kim Philby--in about 1949, officials said. The 49 messages released Tuesday are the first of some 2,200 Venona intercepts that the NSA plans to declassify and make public over the coming year as part of President Clinton’s drive to overcome longstanding resistance within the intelligence community to greater disclosure of old spy secrets that are now a part of history.

The revelations appear to end lingering doubts about the guilt of the Rosenbergs, whose double execution in 1953 led to charges of anti-Semitism and sparked a national controversy that continued long after the end of the McCarthy-era anti-Communist frenzy.

For decades after the Rosenberg trial, the government was criticized both for its decision to seek the death penalty against the parents of two small boys and for basing its case on what critics charged was flimsy, circumstantial evidence. For years, their two sons fought a bitter campaign against the FBI to gain the release of information they hoped would prove that their parents had been framed.

As a result of the government’s desire to maintain the secrecy of Venona, the prosecution in the Rosenberg and other espionage cases of the postwar era used only that evidence against them that could also be obtained through other means. That was enough. The Rosenbergs were found guilty and were executed at Sing Sing prison on June 19, 1953.

Throughout the decades-long debate, intelligence officials never revealed that their case against the Rosenbergs was actually ironclad. They even knew Julius Rosenberg’s KGB code name: “Liberal.”

His KGB handlers, led by KGB officer Leonid Kvasnikov, who headed Soviet atomic espionage in the United States, used that code name for Rosenberg in their requests back to Moscow headquarters for the funds to pay him for his espionage work. One message back to Moscow asked for film for a Leica camera for Rosenberg.

“In connection with the plans for photographing of material by LIBERAL . . . a shortage of cassettes is making itself felt,” said one message. “We cannot get them without a priority. Please order 100 cassettes for a Leica camera . . . and send them on to us without delay.”

“I don’t think they were taking photographs of the Grand Canyon,” quipped Kahn.

Deputy NSA Director William Crowell observed: “In Venona, the FBI used the information unlocked by these code-breakers to develop and conduct their counterintelligence task and to successfully arrest and prosecute the atomic spies.”

Kahn said that Julius Rosenberg was mentioned frequently in the KGB message traffic decrypted by Venona, while Ethel was mentioned only “once or twice.” The degree of involvement of Ethel Rosenberg in the Soviet spy ring has long been a source of controversy. Kahn said that the transcripts don’t provide the final word on that. “Ethel Rosenberg is mentioned less frequently. . . . What this means in terms of her activity is not entirely clear.”

The Rosenbergs’ two sons, Robert and Michael Meeropol, who now live in Springfield, Mass., did not return telephone calls seeking comment Tuesday. They were adopted by songwriter Abel Meeropol after the execution of their parents, and they wrote a 1975 book, “We Are Your Sons,” arguing that their parents were framed.

Ethel Rosenberg’s brother was assigned to Los Alamos as an Army machinist and passed along information on nuclear weapons.

One transcript released Tuesday included lengthy scientific formulas used in atomic research and passed on by spies in America. British physicist Klaus Fuchs was acting as a Soviet agent passing critical information out of the Manhattan Project. Fuchs later confessed to British authorities.

Yet the Venona files are also intriguing for what they could not tell U.S. intelligence officials. The identities of some of the atom spies were never uncovered, including agents code-named Pers and Veksel, figures who have puzzled generations of American spy-catchers.

Hoping to find more useful nuggets about Soviet operations against the United States, the NSA continued to try to complete the decoding of the Soviet messages for decades after the Soviets learned that their communication was compromised. Although most of the decoding was conducted in the late 1940s and early 1950s, the Venona project was not shut down until 1980, when the NSA decided that any Soviet spies that might be mentioned in the aging cable traffic would be either too old or dead.