September 8, 2002 By WILLIAM J. BROAD Adding a startling chapter to the long historical debate over the secret laboratory that developed the atom bomb in World War II, a new book concludes that its leader, Dr. J. Robert Oppenheimer, belonged to the American Communist Party in the late 1930's and early 40's. Contrary to his repeated denials, Oppenheimer belonged to a cell of the party that discouraged members from disclosing their membership, says the book, "Brotherhood of the Bomb: The Tangled Lives and Loyalties of Robert Oppenheimer, Ernest Lawrence, and Edward Teller," by Gregg Herken, a senior historian at the Smithsonian Institution. It is being published today by Henry Holt. The book rests its case on a cache of newly discovered letters, Oppenheimer's reaction to work on an accusatory memoir and the discovery of Communist literature the author links to Oppenheimer. Most of the letters are from Haakon Chevalier, a colleague of Oppenheimer at the University of California at Berkeley. While Dr. Herken says he doubts that Oppenheimer ever spied for the Soviet Union, as some scholars have asserted, it seems likely that he would have been barred from the leadership post if his Communist past had been known. Oppenheimer, who died in 1967 at 62, acknowledged that he had joined many Communist front organizations in the 1930's and that his wife, his former fiancée, his brother and his sister-in-law were all party members. But he denied ever joining the party itself. The issue arose most famously in 1954 at federal hearings over whether his security clearance should be revoked. Though no evidence of his membership was presented, he lost his clearance and influence in the nation's atomic affairs. The new book asserts that Oppenheimer was a member not only of the party but of a secret cell at the University of California that helped set policy and write party literature. Dr. Herken said in an interview last week that he had obtained more confirming evidence since completing the book. About the accusations that Oppenheimer spied for the Soviets, Dr. Herken said: "I don't think he was a spy. The significance of his being a Communist was that it gave him something he had to hide, and may be one explanation of why he was so quiet after 1954" - when the security clearance was revoked. Dr. Priscilla McMillan, an atom historian at Harvard who is familiar with the new book, said Oppenheimer might have seen the unit as a legal and psychological shield that let him claim with some legitimacy that he was no card-carrying member. "The party in those days," Dr. McMillan said, "wanted so much to have some kind of connection to a person of his prominence that they would let you write your own ticket." Dr. Herken details the evidence of Oppenheimer's membership in the book and in documents on his Web site (www.brotherhoodofthebomb .com). The main accuser is Chevalier, who gained notoriety as an intermediary in the Soviet atom espionage rings of the 1940's. Chevalier taught French literature at the University of California at Berkeley, where Oppenheimer taught physics before the government made him director of the envisioned atomic laboratory, which was built in the mountains of New Mexico in 1943 and named Los Alamos. The book says the two men met in 1937 and became close friends, founding a campus branch of a teacher's union and sponsoring benefits for leftist causes. They also joined a secret unit of the American Communist Party made up primarily of Berkeley professors, Chevalier said in letters from the 1960's that Dr. Herken has uncovered. Chevalier wrote from France, where he went in 1950 after being accused of anti-American activities. In one letter, dated July 1964, Chevalier informs Oppenheimer that he is planning to write a memoir referring to the Communist Party cell. He praised the unit's publications as still making "impressive reading" and to credit Oppenheimer with their authorship. He concluded by promising to "do my best" to respect Oppenheimer's wishes if he objected to the goal. "Indeed I do," the physicist replied in a curt letter from Princeton, where he was director of the Institute for Advanced Study. "What you say of me is not true. I have never been a member of the Communist Party, and thus have never been a member of a Communist Party unit." Weeks later, Chevalier wrote to another member of the cell that he "had originally planned to reveal" that Oppenheimer was a Communist, but added, "I decided that I shouldn't, even though the fact is of considerable historical importance." Apparently unaware of Chevalier's decision, Oppenheimer in March 1965 discussed with his lawyer the possibility of enjoining publication of the memoir, according to a record of the discussion Dr. Herken found in Oppenheimer's papers. Chevalier's memoir, "Oppenheimer: The Story of a Friendship," published in 1965, referred to the unit briefly and elliptically as a political "discussion group" but said nothing about its Communist Party ties. Oppenheimer died two years later. Chevalier died in Paris in 1985 at the age of 83, having never written publicly about the secret unit. But Dr. Herken, who visited his daughter in France, found that Chevalier had written an unpublished memoir in which he detailed the story. Dr. Herken tracked down two of the "Reports to Our Colleagues" that Chevalier said the secret unit had published. They were dated Feb. 20 and April 6, 1940, and signed "College Faculties Committee, Communist Party of California," giving no listing of the individual authors. "We know that it would be an evil thing," the first said, "for this country to go to war, or to join a war, against Russia." The second bore a quotation on its cover page from W. H. Auden, one of Oppenheimer's favorite poets: "Hunger allows no choice/ To the citizen or the police:/ We must love one another or die. . . . " Since completing the book, Dr. Herken has continued to track down corroborating evidence. He said a widow of one of the unit's members confirmed in an unpublished memoir that Oppenheimer belonged to the secret group. Dr. Herken said he had also found an elderly person who had helped organize the secret units of the Communist Party in California. Dr. Herken concluded from his research that Oppenheimer was a loyal American. But it is clear, he added, that the physicist never would have won the atom job if his Communist Party membership had been disclosed publicly. "That," Dr. Herken said, "would have been a showstopper." Copyright 2002 The New York Times Company