The Neutron Bomb

Oct. 30, 2017

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.

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Jimmy Carter’s Struggle

The Carter administration, in office for less than six months, was taken by surprise when the “killer warhead” story broke in The Washington Post in June 1977. Carter waited more than a month to make a public statement

on the neutron bomb.

“The enhanced radiation of the neutron bomb has been discussed and also has been under development for 15 or 20 years,” he said at a news conference July 12. “It is not a new concept at all, not a new weapon.” He said that he had “not yet decided whether to advocate deployment of the neutron bomb” but that “it ought to be one of our options.” He forwarded ERDA’s funding request to Congress, adding that “in my present view,” approval was “in the nation’s security interest.”

Sources inside the administration confided later to Richard R. Burt of The New York Times that “from the beginning, Mr. Carter was never comfortable with the controversial weapon, one that apparently challenged his strong personal beliefs over the morality of nuclear warfare.”

The State Department began consultations with the NATO allies. Several of the smaller European nations were dead set against the neutron bomb, but opinions were mixed in West Germany, where the weapons would be based. Apprehension about the neutron bomb was offset somewhat because the Soviet Union had begun deploying a new nuclear missile, the multiple-warhead SS-20, with range to reach all of western Europe.

A major sticking point was that Carter wanted the Europeans to commit to deployment of the neutron bomb before he committed to production. The Europeans wanted him to make the production decision first.

“In effect, the Carter administration decided not to let the Europeans have it both ways,” the Los Angeles Times said. “If they consider the weapon to be militarily useful, the European allies will have to say so publicly and take whatever political heat results from that.”

In November, Congress gave Carter authorization and funding to go ahead with the neutron bomb. The measure passed with minimal debate in the House of Representatives and by voice vote in the Senate.

Media Event

Other news media picked up the chase. The Boston Globe said the neutron bomb was a symbol of “the moral idiocy of military technocrats.” The Nation said it offered “a rare glimpse into the military mind in its most modern convolution.”

Some publications were moderate or even supportive of the neutron bomb but the general effect was inflammatory. Looking back in 1984, after it was all over, a Harvard University study, “The Press and the Neutron Bomb,” said that reports spinning off from The Washington Post led to a political storm in the United States and mass protests in Europe.

As late as August 1977, opinion polls in the United States favored building the neutron bomb by a margin of 44 to 37 percent, but that fell steadily toward 47 percent against it in 1978.

The Soviet Union joined in the outrage, citing “grave dangers for international peace,” and at an arms control conference in Geneva, submitted a draft treaty to outlaw the neutron bomb. At the same time, the Soviets refused to consider any restraint in deploying the SS-20, which the Soviet news agency TASS said had “no relation” whatever to the neutron bomb.

Key NATO leaders were more inclined toward the neutron bomb than they said publicly. In West Germany, Chancellor Helmut Schmidt supported the concept but for political reasons was constrained from getting too far out front.

By March 1978, negotiators had worked out a compromise agreement for production and deployment of the neutron bomb. The arrangement would avoid a Dutch veto and allow tacit acceptance by Italy, Denmark, and Norway. It was to be announced at a meeting of the North Atlantic Council March 20.

Carter, reviewing the draft agreement, was not satisfied and canceled the meeting. According to The New York

Times, “Mr. Carter’s exact reasons for rejecting the alliance plan remain unclear,” but he was said to regard the assurances as “vague” and the commitment as unreliable.

Carter Defers Production

Carter announced his decision to defer neutron bomb production April 7. He said the Pentagon would “proceed with the modernization of the Lance missile nuclear warhead and the eight-inch [artillery] weapon system, leaving open the option of installing the enhanced radiation elements.”

In fact, his position was the result of two separate decisions and much behind-the-scenes wrangling. He made the first decision—not to produce the neutron bomb—in isolation during a fishing trip to Georgia.

Senior Cabinet officials and White House advisors were reportedly “stunned” by this “eleventh hour reversal,” leading to the second decision—adding provisions to defer production rather than cancelling it outright—which repackaged the position for public consumption.

Chancellor Schmidt, who had privately gotten his Cabinet to support neutron deployment, was said to be “deeply embarrassed” and feeling that the Americans had reneged on the bargain. Former President Ford assailed Carter’s decision. Sen. Sam Nunn (D-Ga), a rising star on the Armed Services Committee, called it “a bad mistake that will hurt the NATO alliance.”

The decision was a big victory for opponents of the neutron bomb and anti-nuclear activists in the United States and abroad. Soviet leader Leonid Brezhnev said the USSR would not begin production of neutron bombs either. He invited Carter to join him in a ban on neutron weapons. Carter declined, pointing out that “the Soviets have no use for a neutron bomb” and Brezhnev’s offer had “no significance” since nobody was threatening the Soviet Union with huge tank armies.

In 1978, the United States began work on updated atomic warheads for Lance and the eight-inch artillery, designed so they could be converted into neutron weapons by the insertion of a “special component” which would not be built until a separate decision to do so was made.

Also in 1978, the French, who had remained aloof from the neutron bomb controversy in NATO, revealed that they were considering development of a neutron bomb of their own.

The Reagan Revival

In February 1981, in the first month of the Reagan administration, Secretary of Defense Caspar Weinberger said at a press conference that the United States “very probably” would want to deploy the neutron bomb in Europe.

However, the European allies were not sure they wanted to go down that road again, partly because of their experience with Carter in 1978 and partly because they were now focused on the proposed deployment of the US Air Force’s Ground-Launched Cruise Missile and the US Army’s Pershing II missile to counter the SS-20, which the Soviets were deploying at the rate of one a week.

Like the neutron bomb, GLCM and Pershing II were opposed by leftist demonstrators in Europe. NATO officials preferred to concentrate on that problem instead of diluting their effort to promote the neutron bomb.

Reagan solved the problem for everybody by making the decision himself without asking for any European commitment. In August, he announced that the United States would produce the neutron warheads for Lance and the artillery shell, but would stockpile them in storage in the United States rather than deploy them to Europe.

Reagan’s decision was denounced by the regular group of opponents but Chancellor Schmidt and NATO Secretary General Joseph Luns endorsed it.

Lawrence Livermore Lab designed a third neutron weapon, an artillery shell for the Army’s 155 mm gun. It was a third smaller than the eight-inch shell and had a range of 18 miles. In the end, the decision was for a modernized 155 mm atomic round that could be converted to a neutron weapon with the addition of a special component.

Deployment of GLCM, Pershing II, and the SS-20 continued, but all three types were soon removed from Europe by the Intermediate-Range Nuclear Forces (INF) Treaty in 1987.

In 1982, France began production of a neutron weapon under the presidency of Socialist Francois Mitterand but the program was canceled in 1986 when he was succeeded by his arch-rival, Gaullist Jacques Chirac.


In May 1990, with the end of the Cold War imminent, President George H. W. Bush canceled programs for upgrade replacements for the fission warheads on the Lance missile and nuclear artillery shells in Europe.

In 1992, Bush removed the battlefield nuclear weapons altogether. “The prospect of a Soviet invasion into western Europe, launched with little or no warning, is no longer a realistic threat,” he said in September 1991. “I am therefore directing that the United States eliminate its entire worldwide inventory of ground-launched short-range, that is theater, nuclear weapons. We will bring home or destroy all of our nuclear artillery shells and short-range ballistic missile warheads. We will, of course, ensure that we preserve an effective air-delivered nuclear capability in Europe.”

In 1995, the Army turned over its nuclear warheads to the Department of Energy—which had succeeded ERDA—for destruction. The DOE Pantex Plant in Texas did the dismantling as time allowed between other work, and the last US nuclear artillery shell, a W79 round, was destroyed in 2003.

At peak deployment in the 1960s, the United States had 7,000 tactical nuclear weapons in Europe alone. Only a few such weapons—“nonstrategic nuclear weapons” in current parlance—are left, none of them of the neutron variety.

“The United States now has approximately 760 nonstrategic warheads, with around 200 of them deployed with aircraft in Europe and the remaining stored in the United States,” the Congressional Research Service reported earlier this year. “Estimates vary, but experts believe Russia still has between 1,000 and 6,000 warheads for nonstrategic nuclear weapons in its arsenal.”

The Big Switch

The neutron bomb is seldom mentioned today except in unusual circumstances. One such was in 2012 when John Gilbert rose in the British House of Lords to propose dropping a neutron bomb on the Pakistan-Afghanistan border to create a barrier against terrorists. He said nobody lived there “except for a few goats and a handful of people herding them.” He did not explain what he expected a neutron bomb to accomplish.

By numerous accounts, Israel and China have tested and possess neutron bombs. The strangest case, however, is that of Russia. According to a CIA report in 2000, released with extensive redactions in 2005, the Russians inherited from the defunct Soviet Union a “subkiloton nuclear warhead” enhanced for tailored radiation output and “minimal ecological consequences.”

This weapon, with a yield of about a third of a kiloton, was the result of tests “conducted in the early 1980s to simulate the effects of a US neutron bomb.” The Russians no longer had the overwhelming conventional force advantage that the Soviets did. Their vulnerability was now akin to that of NATO in the 1970s.

The Soviets “would be interested in low-yield warheads because of fears that a future conflict could be waged on Russian soil,” the CIA said. “Russia’s new warheads would inflict less collateral damage.”

That sounds much like the capabilities and purposes of the weapon once decried by the Soviet Union as “the capitalist bomb,” built to kill people and preserve property.


John T. Correll was editor in chief of Air Force Magazine for 18 years and is now a contributor. His most recent articles, “Turning Point at Stalingrad” and “Rolling Thunder,” appeared in the September issue.