The Neutron Bomb

 DECEMBER 2017 JOHN T. CORRELL Print this page  Print this page

 It is almost forgotten today, but the enhanced radiation warhead was a blazing international issue in the 1970s. M110A2 203 mm self-propelled howitzers deployed along a line of trees during Exercise Reforger ’85 near Weitershain, West Germany. The howitzers could fire atomic shells over 20 miles. Photos: US Army via Redstone Arsenal; Courtesy Samuel Cohen; TSgt. Boyd Belcher/DOD via National Archives The neutron bomb controversy exploded suddenly into public notice June 6, 1977, with a headline in The Washington Post: “Neutron Killer Warhead Buried in ERDA Budget.” ERDA, the Energy Research and Development Administration, was the US agency responsible for developing nuclear weapons. The Post front page article—the first of many by reporter Walter Pincus—charged that “the United States is about to begin production of its first nuclear battlefield weapon specifically designed to kill people through the release of neutrons rather than to destroy military installations through heat and blast.” Others quickly joined the chase. The New York Times reported that “the nuclear weaponeers have unfolded a new brainchild, the neutron bomb, which will kill people while preserving buildings, tanks, and artillery.” The uproar over the neutron bomb is largely forgotten today but it was in the news almost constantly in 1977-78 and again in 1981, a blazing international issue that drew in top leaders from the United States, Europe, and the Soviet Union. After almost a year of waffling and indecision, US President Jimmy Carter decided in April 1978 to defer production of the neutron bomb, although he did not cancel the program outright. President Ronald Reagan reopened the question in 1981, eventually electing to produce neutron weapons but to keep them in storage. “Neutron bomb” was the popular term for the enhanced radiation weapon (ERW), a small hydrogen warhead for short-range US Army rockets and artillery shells. It was intended to replace existing nuclear warheads—atomic rather than hydrogen devices—already deployed on battlefield weapons in Europe. Many critics shared the judgment of science fiction author and commentator Isaac Asimov that the neutron bomb “seems desirable to those who worry about property and hold life cheap.” In fact, the purpose had nothing to do with preserving property. The neutron bomb did not leave property intact; by limiting collateral damage, it just destroyed less of it. The objective was to restore the sagging credibility of “tactical nuclear weapons”—as they were then called—as a deterrent against an attack by Soviet and Warsaw Pact tank armies. The critics were closer to the mark with their accusation that the neutron bomb lowered the nuclear threshold by reducing the reluctance to use nuclear weapons. “By giving NATO greater potential to fight a limited nuclear war, will battlefield nuclear weapons increase deterrence, or will they increase the likelihood that NATO may actually engage in nuclear battle?” asked historian Sherri L. Wasserman. The Pincus article in the Post generated a powerful reaction but, as Wasserman noted, it “revealed nothing either deliberately concealed or extraordinarily new about ERWs to Congress or the American public.” Limited-yield nuclear weapons that achieved their main effect from radiation instead of blast and heat were described in considerable detail by a Post article in July 1959. The term “neutron bomb” first appeared in 1959 in US News & World Report, which called it a “death ray” that “would kill man with streams of poisonous radiation, while leaving machines and buildings undamaged.” The neutron bomb was openly debated in Congress between 1960 and 1963. In November 1976, President Gerald R. Ford signed a request from ERDA to fund research and development. Public testimony was heard in Congress in early 1977, although little notice was taken of it. Technocrats regarded the neutron bomb as a straightforward update of battlefield nuclear weapons. Harold Brown, Carter’s Secretary of Defense, was probably right when he said that “without the Pincus articles [neutron warheads] would have been deployed and nobody would have noticed.” Battlefield Atomics In November 1950, President Harry S. Truman announced that use of the atomic bomb in Korea was under “active consideration.” US national strategy in 1953 said that “in the event of hostilities, the United States will consider nuclear weapons to be as available for use as other munitions.” The firebreak between conventional and nuclear weapons came later. The scope of danger was expanded enormously by the hydrogen bomb and its attendant radioactive fallout. Introduction of ICBMs increased the immediacy of the danger and reduced the options for defense against an attack. By the early 1950s, technology made tactical nuclear weapons small and light enough for deployment with battlefield forces. Among the first was the M65 “Atomic Annie,” a huge atomic cannon that required two tractors to move it from place to place. Annie threw an 803-pound warhead and had an effective range of about 20 miles. There were atomic warheads for delivery by rockets, artillery, and aircraft. Incredibly, there were even atomic land mines. Atomic Annie was superseded by guns packing smaller nuclear rounds. The strategic nuclear arena was dominated by the Air Force and Strategic Air Command but battlefield atomic weapons were primarily the province of the Army. In 1956, the Chief of Staff, Gen. Maxwell D. Taylor, reorganized the Army around the “Pentomic” concept. Each combat division had five self-contained battle groups and low-yield tactical nuclear weapons. The most significant of these were the mobile Lance missile, which could fire a one-kiloton atomic warhead for 75 miles, and eight-inch howitzers, with one-kiloton atomic shells and a range of just over 20 miles. By comparison, the yield of the atomic bomb at Hiroshima in 1945 was 15 kilotons; the yield of the Nagasaki bomb was 21 kilotons. NATO, unable to match the overwhelming conventional strength of Soviet and Warsaw Pact tank armies, based its defense on nuclear weapons. At first, it was a matter of “massive retaliation,” in which an attack was to elicit an automatic response by the US strategic arsenal. In 1968, however, under pressure from the United States, NATO adopted a strategy of “flexible response.” NATO would try to turn back a conventional attack with its own conventional forces and tactical nuclear weapons before resorting to the strategic nuclear capability. The Europeans were uneasy with this. It meant a “defense in depth,” with the destruction from the tactical nuclear exchange taking place on NATO territory as the attack rolled westward. The French, disgusted, left the NATO military structure to rely on their independent force de frappe, targeted on the Soviet Union. Sam Cohen’s Invention The battlefield nuclear warheads were getting old and had obvious drawbacks, but deterrence depended on convincing the Soviet Union that NATO was ready to use nuclear weapons to meet an attack. In 1973, the United States began looking seriously for a way to make limited nuclear force in Europe more effective and credible and with less potential damage to western Europe. The search led directly to the neutron bomb. It is generally agreed that the neutron bomb was invented by Samuel T. Cohen of RAND as a consultant to the Lawrence Livermore National Laboratory in 1958. Cohen always claimed that he worked out the concept in 15 or 20 minutes with calculations on a slide rule. The enhanced radiation warhead was a modification of the hydrogen or thermonuclear bomb. Like all hydrogen (or “fusion”) devices, it used a small atomic (or “fission”) bomb as a trigger to set off the hydrogen chain reaction. The neutron bomb would release more of its energy in the form of lethal radiation. Physical damage would be limited to a relatively tight area while the radiation reached further out to penetrate Warsaw Pact armor, which was shielded against nuclear blast and heat. Since the neutron bomb produced little or no radioactive fallout or residual radiation, the target area could be reoccupied within a matter of hours. The neutron bomb was tested successfully in 1962, but to Cohen’s dismay, there were few takers for it. The weapons labs were unable to convince the Pentagon of the merits of replacing the battlefield atomic weapons with costly neutron devices. A neutron warhead was fielded briefly on the Sprint anti-ballistic missile, but was retired in 1975 after only a few months of service when the Sprint system was deactivated. By the middle 1970s, however, the credibility of the battlefield nuclear deterrent was in doubt. In 1976, the Department of Defense asked ERDA to proceed with the W70-3 neutron warhead for the Lance missile and the W79 neutron artillery shell for the Army’s eight-inch gun.