Sam Cohen: Creator of the neutron bomb

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The Independent Online

Cynics called it "the landlord's bomb," that destroyed people, not property. The US government developed it during the Cold War, and later stockpiled it, but ultimately renounced the device, fearful that it would lower the threshhold of full-scale nuclear war. But in the eyes of its inventor Sam Cohen, the neutron bomb was – for at least the first of those reasons – about the most moral weapon ever devised.

Like the bombs dropped on Hiroshima and Nagasaki in August 1945, the neutron bomb relied on nuclear fission. But it was an "enhanced radiation weapon" that caused far less structural damage, relying on a massive output of deadly neutron particles, rather than blast and heat, for its effect. Instead of wiping an entire civilian city off the map, Cohen argued, a nuclear weapon could now be used more discriminately, to wipe enemy soldiers off the battlefield.

Even among the idiosyncratic group of scientists who led America's early nuclear weapons programme, Sam Cohen stood out. He never received an advanced degree, but was extraordinarily creative in his rarefied field. He also loved a joke (not least a Jewish one). But he was irascible, tactless and self-destructively contemptuous of almost every politician.

Asked how friends would describe him, Cohen once replied, "I think they would tell you I'm loyal to them – but a stupid asshole who has gone out of his way to make trouble." As a result, and for all his brilliance, he lost far more battles than he won.

This combative figure was the son of a carpenter from the East End of London of Lithuanian Jewish ancestry, who emigrated to New York where Cohen was born in 1921. The family then moved to Los Angeles, where his father plied his trade building movie sets in Hollywood while Sam took a degree in physics at UCLA before being called up for the army in 1943.

But he never served in uniform. The Army sent him for technical training to the Massaschusetts Institute of Technology, where a talent-spotter recruited him to work on the country's nuclear weapons programme. A fortnight later, Cohen found himself at Los Alamos, New Mexico, plunged into the Manhattan project, rubbing shoulders with Robert Oppenheimer and Edward Teller, not to mention the Soviet spy Klaus Fuchs and David Greenglass, a member of the Rosenberg espionage ring.

Cohen's task was the relativelymodest one of calculating howneutrons behaved in the plutonium fission bomb, code-named "Fat Man", that would destroy Nagasaki on 9 August 1945. That work, however, would later lead him to the concept of the neutron bomb.

After the war Cohen moved to the RAND Corporation, the think-tank set up by the US military to study advanced strategy – in other words, how to wage and win nuclear war. The experience of Hiroshima and Nagasaki did not count; as Cohen would say, "Dropping two atomic bombs on defenseless Japanese cities is not my definition of fighting a nuclear war."

In those early years RAND was at the height of its prestige, among its luminaries the futurologist and nuclear war-gamer Herman Kahn, who had been recruited to the organisation by Cohen. He described Kahn, later held by many to be one of the inspirations for the cinematic Dr Strangelove, as "350lb of brains and black humour."

Cohen's goal, however, was to avoid nuclear Doomsday. His views were strengthened by the Korean War and a visit to semi-obliterated Seoul. As he recounts in his free-wheeeling 1983 memoirs, Shame: Confessions of the Father of the Neutron Bomb, Cohen asked himself, "If we're going to go on fighting these damned-fool wars... shelling and bombing cities to smithereens and wrecking the lives of their surviving inhabitants, might there be some kind of nuclear weapon that could avoid all this?"

The answer he believed, was, yes: the neutron bomb. If it exploded high enough above the ground, the vast amount of neutron radiation emitted would kill people while leaving most structures relatively unscathed. The radiation, moreover, dissipated fairly quickly, unlike the radioactivity of a normal bomb which would leave a site inhabitable for generations or more.

A neutron bomb therefore could be used against enemy forces in the field – against a Soviet tank invasion of western Europe, or better still, Cohen argued, in the war that by the 1960s was unfolding in Vietnam. From then on however, the scientist and the politicians collided. Robert McNamara, the Defence Secretary, decreed that nuclear weapons would never be used in Vietnam. As for Europe, Jimmy Carter intended to deploy neutron weapons, but dropped the idea, in part because of the European left's outrage at the "ultimate capitalist weapon" that destroyed people, not property, but above all from the conviction that if they were used, escalation to all-out nuclear Armageddon was inevitable.

In 1981 Carter's succcessor Ronald Reagan reversed course and announced that neutron bombs would be produced and stockpiled. And about 1,000 were, even though protest from European allies meant they were never deployed. Most upsetting to Cohen, the strategy changed as well. The bombs were to detonate close to the ground, meaning they would be as physically devastating as standard nuclear weapons.

By 2003, the US had reportedly got rid of its neutron bombs. The technology however remains; France, China and Russia have all tested them.

By then Cohen's career was long over. He was fired from RAND in 1969 for continuing to insist that his bomb be used in Vietnam. Subsequently he did government and private consultancy work, while his politics drifted to the right. In 2000, he backed the paleo-conservative, isolationist presidential campaign of Pat Buchanan.

However the controversy over low-yield nuclear weapons persists, most recently over "bunker buster" bombs to destroy targets such as Iran's fortified underground nuclear facilities. And Cohen never lost the faith. As he wrote in typical vein in his 1983 memoir, "Inventing the neutron bomb, for whatever reasons – my upbringing, some bad genes picked up by my great-grandmother in Lithuania who was raped by a Cossack, or something else you might want to toss in – the most moral thing I ever did."

Samuel Theodore Cohen, nuclear scientist: born Brooklyn, New York City 25 January 1921; twice married (two sons, one daughter); died Los Angeles 28 November 2010.