What Edward Teller Did

THE WORLD’S FIRST HYDROGEN BOMB, DESIGNATED MIKE , exploded on November 1, 1952. The test took place on a Pacific island named Elugelab, which ceased to exist within a second of detonation. Mike’s fireball spread fast enough to terrify people 30 miles away who had seen previous nuclear tests. One scientist later described it as “so huge, so brutal—as if things had gone too far. When the heat reached the observers, it stayed and stayed, not for seconds but for minutes.” The fireball, initially a blinding white, expanded in seconds to more than three miles across. Then, glowing purple, it began to rise. At its base a curtain of water fell slowly back into the sea.

Two and a half minutes later a shock wave reached the observers, who heard it as a sharp report. The mushroom cloud rose until it reached the top of the stratosphere, then spread out to form a canopy a hundred miles across. Down below, there was a deep crater in the ocean floor. Two hours later a jet pilot flew his plane into the mushroom’s stem and saw it glowing like the interior of a furnace. A survey team found fish whose skin was burned away on one side, as if they had been dropped into a frying pan.

The physicist Edward Teller, whose work had led to this explosion, was across the Pacific at the University of California in Berkeley. When the appointed hour of detonation drew near, he went to the basement of the geology building and watched a point of light on a seismograph. “At exactly the scheduled time I saw the light point move,” he later wrote. He sent a telegram to colleagues at the Los Alamos nuclear laboratory in New Mexico who had designed and built the bomb. The message read, “It’s a boy.”

Teller’s road to this strange paternity began in Budapest, Hungary, where he was born in 1908. Eleven years later, in the aftermath of World War I, his country fell under the Communist dictatorship of the strongman BeIa Kun. The new regime billeted two soldiers in the Tellers’ home, where they terrified the family by searching for forbidden hoards of currency.

After a few months this revolution quickly brought a counterrevolution, led by the fascist Miklós Horthy. Kun and many of his commissars had been Jewish, and the Tellers were Jewish too. Horthy’s regime, which would last well into World War II, drove tens of thousands of Jews into exile while building torture chambers and executing at least 5,000 people. The Tellers managed to remain in Budapest, but the Kun and Horthy dictatorships left a lasting mark on young Edward Teller. For the rest of his life he would have a passionate hatred of totalitarianism and a fierce determination to build defenses against it.

He showed a great talent for physics. After studying in Karlsruhe and Munich, in Germany, he went to the University of Leipzig. There he worked with Werner Heisenberg, a founder of quantum mechanics. He was awarded his Ph.D. in 1930 and won a position at the University of G’f6ttingen, one of the world’s best centers for research.

Then in 1933 Hitler came to power. Teller had no doubt about what was coming. He decamped to Denmark in early 1934 and joined Niels Bohr (who had won a Nobel Prize in 1922 and whose work complemented Heisenberg’s) at the Copenhagen Institute for Theoretical Physics, which Bohr had founded in 1919. In the fall of 1934, Teller went to the University of London as a lecturer in chemistry, and in August 1935 he left for the United States, where he took a full professorship at George Washington University.

He had now seen totalitarianism at first hand in both Hungary and Germany. He escaped by developing an active interest in the nuclear reactions that power the sun and stars. Similar reactions would eventually provide the energy of a hydrogen bomb, but thoughts of such weapons still lay well in the future.

For a long time the profession of physics had been as rarefied and unworldly as the priesthood, but after the discovery of atomic fission in Germany in 1938, its practitioners began to deal with politicians and generals. The threat of war lent particular urgency to fission research. Albert Einstein’s famous 1939 letter to President Franklin D. Roosevelt brought a small appropriation, which was followed by a research program that later became known as the Manhattan Project.

Teller accepted a personal call to arms in 1940, as Nazi tanks were unleashing their blitzkrieg on the Low Countries. On May 10 Roosevelt addressed a meeting of scientists in Washington, and Teller listened earnestly to the President’s words: “If the scientists in the free countries will not make weapons to defend the freedom of their countries, then freedom will be lost.” He heard this speech as a summons to duty, and he later declared, “I had the strange impression that he was talking to me. My mind was made up, and it has not changed since.”

He and his colleagues knew of the work of the physicist Hans Bethe, who in 1938 had described the fusion reactions that power the sun. Nuclear fusion, like nuclear fission, involves the conversion of mass to energy. But while fissionworks by splitting one atomic nucleus into two (with the products having less mass than the initial nucleus), fusion works by merging two nuclei together into one (with the product, again, having less mass than the individual nuclei). Under the intense heat and pressure of the deep solar interior, the reactions described by Bethe convert hydrogen into helium at a rate of more than 600 million tons per second. Scientists also knew that deuterium, a heavy isotope of hydrogen, underwent fusion particularly readily. This isotope could be extracted from ordinary water.

Italy’s Enrico Fermi, a leading experimentalist, was part of the nascent weapons community. One day in September 1941, as he and Teller walked across the campus of Columbia University (where both had recently joined the faculty), Fermi suggested that recent developments could make it possible to duplicate on earth the fusion in the sun’s interior. An atomic bomb (which still existed only in theory) might heat a mass of deuterium, Fermi said, and cause it to undergo reactions like those inside the sun. Teller found the idea fascinating and explored it with calculations. As he later recalled, “I decided that deuterium could not be ignited by atomic bombs. I reported my results to Fermi and proceeded to foreet about it.”

During the summer of 1942, J. Robert Oppenheimer, the head of the Manhattan Project, hosted a gathering of physicists at Berkeley. Teller fell in with a young colleague, Emil Konopinski, who was eager to study a fusion bomb. Konopinski suggested using not only deuterium but also tritium, an even heavier isotope of hydrogen. Tritium does not exist naturally on earth, but Konopinski thought it might be created within the bomb itself, by nuclear reactions that involved lithium. Teller tried to show him that this would not work. They made new calculations, and as Teller describes it, they learned that “the roadblocks I had erected for Fermi’s idea were not so high after all. We hurdled them one by one and concluded that heavy hydrogen actually could be ignited by an atomic bomb.”

The idea drew full attention from Oppenheimer’s summer study group. The physicists concluded that a bomb of this type might yield the energy of a hundred million tons of TNT Such a weapon would be thousands of times more powerful than the projected atomic bomb. Even so, therewas no prospect of bypassing the A-bomb, since it would have to serve as an igniter for the H-bomb (or Super, as it was called). Attention focused anew on the A-bomb, with the H-bomb as a topic for the distant future.

In 1943 Oppenheimer led a number of his colleagues to a new and highly secret research center at Los Alamos, New Mexico. Teller was one of them. His collaborator Stanislaw Ulam remembers him as “a warm person” who “clearly desired friendship with other physicists.” Oppenheimer took advantage of this trait, assigning him to introduce newcomers to the laboratory.

Teller was warm and open, but Ulam also recalls him as “always intense, visibly ambitious, and harboring a smoldering passion for achievement in physics.” Teller had assisted Oppenheimer in organizing the work at Los Alamos and recruiting its staff members. The plans called for a theoretical division, which Teller hoped to direct. Instead, he found himself passed over in favor of Bethe. Bethe later said that his selection “was a severe blow to Teller, who had worked on the bomb project almost from the day of its inception and considered himself, quite rightly, as having seniority over everyone then at Los Alamos, including Oppenheimer.” Bethe believed he was chosen because he had skill in administration.

Teller was particularly unhappy because he was now removed from day-to-day contact with Oppenheimer, whom he admired. He responded by taking on the design of an H-bomb as his own personal challenge. He contributed to mainstream A-bomb studies, but he spent as much time as he could on the H-bomb, even after the war ended with the atomic bombings of Hiroshima and Nagasaki.

The design Teller favored amounted to a stick of nuclear dynamite. An A-bomb would serve as its detonator, providing a burst of energetic neutrons for ultra-rapid heating. This would ignite thermonuclear reactions in a long pipe filled with liquid deuterium. A small quantity of tritium, produced separately in a nuclear reactor, would react with the deuterium, and a wave of nuclear fusion would sweep down the pipe, producing the blast of the H-bomb.

This arrangement became known as the “classical Super.” Initial calculations made with the University of Pennsylvania’s ENIAC computer in 1945 and 1946 suggested that it might work—if one ignored some possible complicating side effects. The pertinent computations were very demanding, and computers were still in their infancy, so many assumptions and approximations had to be made. This gave Teller leeway to tailor the calculations in a way that promoted his approach.

With the war over, the staff at Los Alamos, like the nation’s soldiers and sailors, wanted to go home. Bethe went back to Cornell; Oppenheimer went to Caltech for a year, followed by a year at Berkeley and then a position at the Institute for Advanced Study, in Princeton, New Tersev. A new lab director, Norris Bradbury, offered Teller the directorship of the theoretical division. Teller wanted it, but only if he could lead a major push toward building an H-bomb. This proved impossible because of postwar cutbacks. He therefore joined the general exodus, taking a position at the University of Chicago alongside his old friend Fermi.

At first, he was still militant and ready to oppose tyranny with arms. Bethe recalls that a few months after the war, “Teller said we had to continue research on nuclear weapons. … The war was not over and Russia was just as dangerous an enemy as Germany had been.”

But in Chicago, back in the academic world, his restless soul found peace for a while. His wife, Mici, had a second baby, and he spent more time with his family. With America holding a nuclear monopoly, he shared the widespread hope of lasting peace. He agreed “that the effects of an atomic war will endanger the survival of man.” He praised the Baruch Plan for international control of atomic weapons, and he wrote of “world law and world government,” which “alone can give us freedom and peace.”

Then reality set in. In 1948 the Soviets took control of Czechoslovakia, consolidated a takeover of Hungary, and tried to seize West Berlin by blockading that city. Totalitarianism was on the march again, and again Teller felt it personally. His parents and other family members had survived the Nazi occupation and were still in Budapest, but now they were cut off from him. He responded by leaving Chicago and returning to Los Alamos in July 1949 to build weapons.

In August 1949, the Soviets set off their first atomic bomb. A month later, in Beijing, Mao Zedong proclaimed the People’s Republic of China. With the Soviets already in control of Eastern Europe, these events raised the specter of a nuclear-armed communist bloc commanding the almost limitless manpower of the Chinese. The Cold War had reached the fever pitch at which it would remain through the 1950s and early 1960s.

In Washington, President Harry S. Truman prepared to respond with a stepped-up nuclear program. Oppenheimer chaired the General Advisory Committee of the Atomic Energy Commission (AEC), which was a key source of advice. The committee met in late October 1949 and endorsed plans for expanded production of plutonium and fissionable uranium, for development of battlefield nuclear weapons, and for research on fission bombs of novel design. However, the group’s members came out strongly against proceeding with work on the H-bomb. They were convinced that the existing stockpile of fission weapons, which would soon be greatly increased, would be enough to protect the nation. They argued that this would still be true even if the Soviets built H-bombs of their own. Moreover, thev raised ethical concerns.

The committee’s majority asserted that the H-bomb’s use “would involve a decision to slaughter a vast number of civilians. … a super bomb might become a weapon of genocide. … We believe a super bomb should never be produced.” A minority report, signed by Fermi and Isidore I. Rabi, went further: “The fact that no limit exists to the destructiveness of this weapon makes its very existence … a danger to humanity as a whole. It is necessarily an evil thing considered in any light.”

But Teller knew his way around Washington, and he had support where it counted. Among the people who wanted an H-bomb were Sen. Brien McMahon, chairman of the Joint Committee on Atomic Energy; Robert LeBaron, a deputy secretary of defense who chaired the military liaison committee of the AEC; and Lewis Strauss, a former investment banker and now an AEC commissioner. These men, none of whom were physicists (though LeBaron had worked as a research chemist), viewed the Super as the main element of America’s answer to the Soviet atomic bomb.

In January 1950, Truman announced a greatly enlarged nuclear program. He publicly directed the AEC “to continue its work on all forms of atomic weapons, including the so-called hydrogen or superbomb.” Yet while Teller had gotten the green light he wanted, no one actually knew how to build a hydrogen bomb, for studies had failed to prove that the classical Super was feasible. During 1950 new and more accurate computations showed clearly that there was no way the classical Super could work. The deuterium simply would not get hot enough.

Help came from a technique employed in atomic bombs that worked by implosion. The bombs used a sphere of plutonium within a thick shell of high explosives; detonation of the chemical explosives produced a powerful shock wave that traveled inward, compressing the plutonium and touching off the nuclear blast. Teller had considered a similar scheme for hydrogen bombs, using implosion to compress deuterium, but chemical explosives would be too weak, and he could not figure out how to use the much greater energy of an atomic bomb for this purpose.

Then, early in 1951, the mathematician Stanislaw Ulam weighed in with a suggestion. Ulam had made some of the recent calculations that had killed the classical Super, and now he was back working on atomic bombs. He proposed a novel two-step design in which the neutrons produced by exploding one A-bomb could be made to implode a shell of plutonium, thus setting off a second and much larger A-bomb with extraordinary yield.

Ulam pursued this approach and soon saw that it could also achieve very high compression of liquefied deuterium in a hydrogen bomb. That approach would have a much better chance of initiating fusion than Teller’s scheme, which essentially relied on ordinary heat transfer. Ulam took the idea to Teller, who at first was skeptical. But Teller took up the idea and improved on it. He was aware that in addition to neutrons, atomic bombs also release X rays, a form of radiation that would be far more useful for imploding the deuterium.

In the final design, a large cylinder of liquid deuterium was to be surrounded with a thick layer of uranium. At detonation, X rays from the atomic trigger, or “primary,” would be directed onto the surface of the uranium. This would blow off its outer layers with enormously explosive force, which in turn would place the rest of the uranium layer under extreme pressure, compressing it along with the liquid deuterium that lay within. At the center of the cylinder of deuterium was a rod of plutonium, which would be compressed beyond the critical point by the deuterium and undergo an explosion of its own, boosting the yield greatly.

This approach to H-bomb design became known as the Teller-Ulam principle. It was a true breakthrough and was quite unexpected. Bethe wrote that this concept was “about as surprising as the discovery of fission had been to physicists in 1939.” Oppenheimer put aside his own reservations: “When you see something that is technically sweet, you go ahead and do it.”

The Mike test showed the value of this principle on the first try. Mike delivered 10.4 megatons of explosive yield, nearly a thousand times as much as the atomic bomb detonated at Hiroshima. It did not demonstrate a militarily useful weapon; it weighed 82 tons and relied on liquid deuterium, which was hard to handle. But Teller’s colleagues quickly crafted new bomb designs that replaced this deuterium with lithium deuteride, a powder that resembled table salt. This led to true hydrogen bombs that were not only very powerful but also light in weight.

Teller had long since put aside his musings on world government. When seeking a crash program for the Super, he had predicted that unless the project went forward quickly, the Russians would invade the United States and take him prisoner. He came to see any opposition to him or his hydrogen bomb as a form of opposition to the national interest. Oppenheimer had been the leader of the H-bomb’s opponents, and after Teller had gotten his Super program approved, he began working to orchestrate Oppenheimer’s downfall, on grounds that he was a security risk.

Oppenheimer’s wife, brother, sister-in-law, and former fiancée all had been members of the Communist party. Even so, he had held high-level security clearances for more than a decade. But by 1950 it was clear that Soviet agents had walked off with a trove of secrets from Los Alamos while Oppenheimer was in charge. These revelations called his trustworthiness into question.

In May 1952, Teller met twice with an FBI agent and made a number of allegations against Oppenheimer. These were included in a bill of particulars to which Oppenheimer would have to respond. A year later Lewis Strauss became chairman of the AEC, the third man to hold that job, and he took a strong stand against Oppenheimer. In November 1953, William Borden, a fierce nuclear hawk who was executive director of the Joint Congressional Committee on Atomic Energy, wrote a letter to J. Edgar Hoover, director of the FBI. In it he stated: “More probably than not, J. Robert Oppenheimer is an agent of the Soviet Union.”

In April 1954 Oppenheimer faced a formal hearing. This revealed that he had lied to a government investigator eight years earlier to protect a friend who was implicated in espionage. Teller appeared at the hearing and gave his own views: “If it is a question of wisdom and judgment, as demonstrated by actions since 1945, then I would say one would be wiser not to grant clearance.” Teller’s testimony did not make the difference; Oppenheimer himself had provided the rope that hanged him. Still, his banishment was the result Teller had actively sought.

Was Oppenheimer really a spy? Even in 1954 no one charged that he had knowingly hired agents. The subsequent years have seen much new material come to light concerning such high-level Soviet agents as Alger Hiss and Harry Dexter White. None of these disclosures contain any mention of Oppenheimer. Still, he had lied to protect his friend. In the superheated climate of suspicion that prevailed in 1954, that was enough to bring him down.

Although Oppenheimer lost his security clearance, he continued to hold the deep esteem and affection of the physics community. For his part in bringing about Oppenheimer’s downfall, Teller faced reprisals. At Los Alamos, a few days after Teller’s testimony became public, an old friend looked at him stonily and turned away. It was the start of a general ostracism. Teller later declared that “more than ninety percent” of his professional colleagues considered him “an enemy, an outcast. It had a profound effect.”

A few old friends continued to stand by him, but in subsequent years he became increasingly isolated from the community of weapons physicists. He turned to a circle of right-wing conservatives, military leaders, and personal protégés. He had already won Air Force support for establishment of a second AEC weapons laboratory, separate from Los Alamos. The new center, Lawrence Livermore National Laboratory, was named for Ernest Lawrence, the inventor of the cyclotron and a Nobel laureate at the University of California at Berkeley. It was built near the town of Livermore, California, and stood within easy driving distance of Berkeley, with which it was affiliated. Teller intended the new laboratory, which opened in 1952, to compete with Los Alamos, challenging its monopoly in nuclear-weapons design. Although he was not the laboratory’s director, he ran the show. He handpicked his acolytes for the top positions and managed the laboratory as his personal fief.

Los Alamos and Livermore became fierce rivals. Harold Agnew, who had been at Los Alamos since the beginning and served as its director from 1970 to 1979, recalled in 1985 that “at Los Alamos, our feeling was always that our primary problem was Livermore and not the Soviet Union. Livermore started late; they had to play catch-up. Their early endeavors did not prove to be very successful.” Several of these early weapons designs were duds that failed to go off, and Livermore lost in initial design competitions to select warheads for the nation’s early ballistic missiles. “We wiped ’em,” Agnew remembered. “Every one—Thor, Jupiter, Atlas, Titan—every warhead was from Los Alamos.”

But Livermore and Teller scored a coup with the warhead for the submarine-based Polaris missile. It required particularly low weight, which Teller achieved through lavish use of weapons-grade uranium (which, though heavy itself, allowed each pound of the bomb to explode with far more energy). This approach took advantage of a burgeoning supply of uranium, and Agnew notes that “it just wasn’t in line with our culture. We had been brought up in a culture of scarcity in the use of nuclear materials. Edward’s idea was like putting butter on both sides of the bread. And he got one hell of a yield.”

At Livermore the Teller-Ulam principle was a specialty of the house. This principle, again, called for enclosing a charge of lithium deuteride within a thick shell, or pusher, which would then be compressed inward. In warheads, the energy burst needed for compression came from an A-bomb, but other applications might use a different energy source, possibly even one that could fit within a laboratory. This raised the question, On how minute a scale could the Teller-Ulam principle work? To put it another way, how small could an H-bomb be?

As early as 1957, the Livermore physicist John Nuckolls began making calculations. He saw that this topic offered a possible approach to laboratory-scale H-bomb detonations, which could give new insight into weapons physics. It also offered a potential route to controlled fusion, perhaps through the rapid-fire detonation of small pellets filled with deuterium and tritium. Just as atomic fission, the process behind the atomic bomb, could be harnessed and used to generate electricity, so too might the much greater power of nuclear fusion be applied to civilian use.

Nuckolls left open the issue of what energy source might detonate the pellets. He didn’t think to use lasers, because they hadn’t been invented yet. Even so, by 1960 he had designs that promised to shrink the H-bomb to a device the size of a child’s marble for use in generating energy. “I worked out the power, the energy, the focusing that had to go with it,” Nuckolls recalls. “I had all these parameters worked out at the time the laser was invented. It was as though I had fashioned a wagon and somebody marched a horse along.”

Lasers eventually emerged as the energy source of choice, but it took time for them to become powerful enough for this demanding task. Around 1970 the necessary technology finally appeared to be available. This brought construction of the world’s largest laser, named Shiva. Shiva filled a room the size of a basketball court, but it flopped, delivering barely one-fourth of its planned power. Livermore’s managers responded by building a new laser, Nova, but its pellets also failed to ignite. In 1976 Teller recommended against “uncontrolled expenditures on controlled fusion” by the federal government.

With his Teller-Ulam principle, Teller now had a hit and a miss. He had scored a home run with the hydrogen bomb, but Livermore’s work in laser fusion fell considerably short of success. The laboratory’s overall record was similarly mixed. Its greatest success came at the triple point where physics, weapons design, and defense policy converge. Three Livermore directors—Herbert York, Harold Brown, and John Foster—served within the Pentagon in the highly demanding post of director of defense research and engineering. Brown also became president of CaItech and President Jimmy Carter’s Secretary of Defense.

These men cherished their ties to Teller, who maintained his influence in Washington through eight administrations. During the 1980s, having retired to a position as a fellow of the Hoover Institution at Stanford University, Teller blazed forth anew, as he pursued a long-standing interest in defense against missile attack. His hopes took shape as the Strategic Defense Initiative (SDI), which was soon derisively nicknamed Star Wars.

The Pentagon had pursued missile defense since the 1950s. Its approach called for quick-firing rockets that would use atomic bombs to knock out incoming warheads. However, such weapons would produce an “electromagnetic pulse,” a powerful surge of voltage that would fry the electronics of a nation’s missile-guidance systems, as well as telephones, power transmission, and other civilian technology. No one ever found a way around this, in the United States or the Soviet Union. This roadblock encouraged the superpowers to negotiate the Anti-Ballistic Missile Treaty of 1972, in which they pledged to observe extremely severe limits on missile defenses.

This treaty did permit research on new methods of strategic defense, and by 1980 Teller had his eye on a promising one, the X-ray laser. It would use an array of carefully designed rods, each independently aimable and able to produce a missile-killing burst of concentrated X rays. A small nuclear bomb would provide these laser rods with the necessary energy. Livermore was the center for work on this concept, and an initial test, called Dauphin, took place in November 1980. In this test an instrumented nuclear bomb was detonated deep underground. It seemed to show that an X-ray laser would work.

By then Ronald Reagan had been elected to replace Carter in the White House. Reagan had met Teller in late 1966, and they shared a concern for missile defense. Teller quickly showed his influence as Reagan chose another of his protégés, George Keyworth, as the White House science adviser.

Reagan was under strong political pressure to take a new initiative in the arms race. Some of his Democratic critics favored a nuclear freeze, which the President viewed as tantamount to unilateral disarmament. In a nation wide address in March 1983, he announced his alternative, SDI. Within this new program the X-ray laser stood as a centerpiece.

Other types of missile defense were under consideration, including conventional lasers to be placed in orbit, particle beams, and “smart rocks”: weapons resembling precisely guided cannonballs that would home in on enemy warheads. But these existed only on paper or as small-scale laboratory experiments, whereas the Dauphin test seemed to suggest that X-ray lasers could soon be operational weapons. Moreover, they promised far more power than rival methods of missile defense. By launching laser-bearing missiles from submarines, SDI avoided the possible need to place large battle stations in orbit.

A second “shot,” or underground nuclear test, codenamed Romano, took place in December 1983. It seemed to give further evidence that the X-ray laser would indeed work. The Cottage shot in March 1985 even suggested that the X rays could be focused for greater intensity. However, these promising results soon came under attack. Physicists at Los Alamos showed that the purported X-ray measurements actually represented radiation from impurities in a component of the instruments used for observation. In December 1985 the Goldstone shot confirmed this finding. The basic X-ray laser proved to be only one-tenth as bright as expected, making it useless for missile defense. Further work proved focusing to be an illusion as well.

That did it. It was now clear that an X-ray laser would demand many more shots and far more time, if it could be built at all. The Star Wars program went downhill, along with Teller’s influence. In 1993, with communism having imploded and with a Democrat back in the White House, Teller was out of the picture completely. Today he remains a fellow of the Hoover Institution, but his days of glory are long gone.

How, then, can we sum up the Edward Teller of Cold War days? Was he a Dr. Strangelove? For what it’s worth, Teller’s personal life was almost boringly normal. He and his wife had fallen in love as teenagers, and they shared a strong and enduring marriage. He did not work as a recluse but cherished the company of friends. Yet he was not emotionally secure; he had an unnerving tendency to take things personally. This colored his view of the Soviets. When Oppenheimer opposed him, he treated the policy disagreement as an attempt to sabotage the H-bomb project and reported his suspicions of disloyalty to the FBI.

He never came close to a Nobel Prize. His professional contributions did not approach those of Heisenberg, Bethe, Fermi, or Bohr. As a physicist, he had only one really good idea during his career, the Teller-Ulam principle, and the subsequent success of his H-bomb became an exercise in irony. At the outset, it offered the prospect of weapons with unlimited yield. This might have led to large ships carrying thousands of tons of lithium deuteride sailing the seas or submerged on the seabed. Such weapons, able perhaps to wipe out a continent at one blow, would have amounted to the “doomsday machine̵ foreseen by Herman Kahn, a leading expert in nuclear strategy.

In fact, the advent of precision-guided ballistic missiles during the 1960s and 1970s pushed weapons design in the oppositte direction, toward lower weights and diminished yields. Early ICBMs were inaccurate; they relied on powerful H-bombs to destroy a target by blowing away everything that lay between the aim point and the impact point. Improvements in guidance spurred a push toward smaller warheads that had no need for such destructive power. The missiles themselves became smaller, too, and thus could be better protected. They were deployed in silos that could ride out a nuclear strike, or aboard submarines. This reduced the danger of nuclear war by allowing national leaders to hold their fire rather than launch too soon.

Teller’s other major initiatives, laser fusion and Star Wars, were not successful. Unlike nuclear fission—which, though it never yielded power “too cheap to meter,” has had numerous useful nonweapons applications, from naval propulsion to medical isotopes—fusion has given the world no important spinoffs. Even so, however, Teller’s dead ends represented concepts of such significance that they were well worth pursuing, even amid serious risk of failure.

Controlled fusion remains an active area of research, for if it can ever be achieved, it offers a truly inexhaustible energy source. Equally important, the failure of Teller’s SDI has finally placed out of reach an impenetrable, continent-spanning missile defense. (The United States does, however, continue to investigate small-scale shields to protect against potential attacks of a few missiles from such states as North Korea, Iran, and Iraq.) This makes obsolete the strategy of overkill, under which the Soviets and Americans deployed far more missiles and warheads than they could plausibly need, in order to make sure that some of them would get through. By trying unsuccessfully to build a large-scale missile defense, Teller and his disciples have advanced the prospects for major reductions in nuclear arms. That, rather than his weapons, may prove in the end to be Teller’s most lasting legacy.