On June 27, 1945, after almost a year at Oak Ridge, Koval was transferred to a top-secret laboratory in Dayton, Ohio. This may have been his most damaging placement; it was there that the polonium-based initiator went into production. Once again, Koval was designated a health physics officer, free to roam the installation.
That July 16, the initiator passed a crucial test: the world's first atomic bomb exploded at a site called Trinity within the bombing range in Alamogordo, New Mexico. This was the explosion that prompted J. Robert Oppenheimer, the scientific director of the Manhattan Project, to quote the Bhagavad-Gita: "I am become death, the destroyer of worlds." It gave U.S. war planners the confidence to deploy a plutonium-based bomb, in addition to the uranium-based one in their arsenal.
By then, Germany had surrendered, but Japan had not. Just three weeks later, on August 6, 1945, the uranium-based bomb was detonated over the city of Hiroshima, killing 70,000 people immediately and 70,000 more by the end of the year. And on August 9, 1945, a replica of the Trinity bomb exploded over Nagasaki. Five days later, Japanese Emperor Hirohito announced his nation's surrender.
Amid the devastation of the two cities, there were widespread calls for a ban on nuclear weapons. The United States and the Soviet Union proposed an international system of nuclear arms control, but that never happened. Indeed, the Soviets intensified an atomic-bomb program they had begun during the war. As early as October 31, 1946, the CIA estimated that they would succeed "some time between 1950 and 1953"; as the months passed that estimate tilted more toward 1953.
But on August 29, 1949, the Soviets detonated their first atomic bomb, at their Semipalatinsk Test Site in Kazakhstan. The device was a plutonium weapon. Not until 2007 did Russian military officials disclose one crucial factor in their accelerated achievement: the initiator for that bomb was "prepared to the 'recipe' provided by military intelligence agent Delmar—Zhorzh Abramovich Koval," the Defense Ministry newspaper Krasnaya Zvezda reported when Koval received his gold star.
In 1949, President Harry Truman calmly apprised the American public of the Soviets' test. "We have evidence that within recent weeks an atomic explosion occurred in the USSR," he announced on September 24, in a statement of 217 words, not one of which was "bomb" or "weapon." "Ever since atomic energy was first released by man, the eventual development of this new force by other nations was to be expected," he said. "This probability has always been taken into account by us." Behind the scenes, however, nuclear scientists, generals and policy makers were furiously debating whether the United States should push for arms control or for the next generation of nuclear weapons. Truman rendered that debate moot in January 1950, when he authorized the development of a hydrogen bomb. The nuclear arms race had begun in earnest.
Given that George Koval used his real name, it is tempting to wonder why he didn't fall under suspicion as a security risk until long after it was too late. (Klaus Fuchs was caught after the war, implicated in the same group of intercepted Soviet cables that exposed the Rosenbergs and others. Fuchs served more than nine years in a British prison and then emigrated to Dresden, where he died at age 76 in 1988.) Scholars and analysts are still trying to find out why Koval went undetected.
One reason may be that the Soviets were U.S. allies at the time; counterintelligence efforts were focused on German agents. Another is that interservice rivalry hobbled the Manhattan Project's efforts to vet its scientists. According to Kramish and others, Gen. Leslie Groves, the military director of the Manhattan Project, did not trust the FBI to do security checks on the scientists, preferring to rely on Army counterintelligence officers. A third possibility is that in wartime, the Allies chose scientific talent over pristine clearance records. "People like Oppenheimer had all sorts of questionable connections. The question was: What do you do about it?" says Jon Lellenberg, a retired policy and strategy official with the Office of the Secretary of Defense. "If Oppenheimer was as essential as he seemed, and as committed to success as he was, it was probably deemed worth some political risk for the sake of the program."
And finally, there was the timing: by 1949, when the Soviets exploded their bomb, George Koval had left the United States.
His exit was unhurried. Honorably discharged from the Army in 1946, he returned to the Bronx and to CCNY. He joined Eta Kappa Nu, an electrical-engineering fraternity, and received his bachelor's degree in electrical engineering cum laude on February 1, 1948. A few months later, he told friends that he was thinking about going abroad, to Poland or Israel. According to Norris, Koval secured a U.S. passport for six months' travel to Europe on behalf of a company called Atlas Trading. That October he sailed for Le Havre aboard the ocean liner America, never to return.