Hiroshima was destroyed in a flash by a bomb dropped from a propeller-driven B-29 of the U.S. Army Air Force, on the warm morning of Monday, August 6, 1945. The bomb was not chemical, as bombs until then had been, but rather atomic, designed to release the energies Einstein described. It was a simple cannon-type device of the sort that today any number of people could build in a garage. It fell nose-down for forty-three seconds, and for maximum effect never hit the ground. One thousand nine hundred feet above the city the bomb fired a lump of highly enriched uranium down a steel tube into a receiving lump of the same refined material, creating a combined uranium mass of 133 pounds. In relation to its surface area, that mass was more than enough to achieve “criticality” and allow for an uncontrollable chain of fission reactions, during which neutrons collided with uranium nuclei, releasing further neutrons in a blossoming process of self-destruction. The reactions could be sustained for just a millisecond, and they fully exploited less than two pounds of the uranium before the resulting heat forced a halt to the process through expansion. Uranium is the heaviest element on earth, almost twice as heavy as lead, and two pounds of it amounts to only about three tablespoonfuls. Nonetheless, the explosion over Hiroshima yielded a force equivalent to 15,000 tons (fifteen kilotons) of TNT, achieved temperatures higher than the sun’s, and emitted light-speed pulses of dangerous radiation. More than 150,000 people died.
Three days later, the city of Nagasaki was hit by an even more powerful device—a sophisticated implosion-type bomb built around a softball-sized sphere of plutonium, which crossed the mass-to-surface-area threshold of criticality when it was symmetrically compressed by carefully arrayed explosives. A twenty-two-kiloton blast resulted. Though much of the city was shielded by hills, about 70,000 people died. Quibblers claim that a demonstration offshore, or even above Tokyo harbor, might have induced the Japanese to surrender—and if not, there was another bomb at the ready. But the idea was to terrorize a nation to the maximum extent, and there is nothing like nuking civilians to achieve that effect.
The physicists who had developed these devices understood the potential for miniaturization and a simultaneous escalation in warhead yields, past the twenty-two kilotons of Nagasaki and indeed past a thousand kilotons, into the multimegaton range—the realm, when multiplied, of global suicide. Moreover, they realized that the science involved, however mysterious it seemed to outsiders, had already devolved into mere problems of engineering, the knowledge of which could not be contained. Within a few years humanity would face an objective risk of annihilation—a reality that compelled those who understood it best to go public with the facts. In the months following Japan’s surrender, a group of the men responsible for building the bomb—including Albert Einstein, Robert Oppenheimer, Neils Bohr, and Leo Szilard—created the Federation of American (Atomic) Scientists (FAS), to disseminate nuclear-weapons information. Washington at the time harbored the illusion that America possessed a great secret, and could keep the bomb for itself to drop or not on others. The founders of FAS disagreed. The current vice president of its Strategic Security Project, an affable scientist named Ivan Oelrich, recently said to me, “The biggest secret about the atomic bomb was whether it would work or not.” But after the United States exploded one, there was no longer any question in the minds of other countries. “They knew that if they did X, Y, and Z, they would have success. So in 1945 the scientists who founded this organization said, ‘Look, there is no secret. Any physicist anywhere can figure out what we did and reproduce it. There is no secret, and there is also no defense.’”
Some of the solutions they proposed may seem quaint. Albert Einstein, for instance, called for the creation of an enlightened world government, complete with the integration of formerly hostile military staffs and the voluntary dismantling of sovereign states. But the founders of FAS were not naive so much as desperate and brave. They said, in essence, If you knew what we know about these devices, you would agree that at any price, the practice of war must end. It was a rare call for radical change by men at the top of their game. But history shows that the future is impossible to predict. There was no exception here. After sixty years there has been no apocalypse, and a nuclear peace has so far endured for all the wrong reasons—an unenlightened standoff between the nuclear powers, each of them restrained from shooting first not by moral qualms, but by the certainty of a devastating response. Moreover, the very lack of defense that worried the scientists in 1945 turned out to be the defense, though treacherous because it required tit-for-tat escalations. But these are latter-day corrections to the concerns of enormously competent men, and their message is equally valid today. Detailed knowledge of nuclear-bomb making has escaped into the public domain, and the use of even a single fission device could pose an existential threat to the West.
Last winter in Moscow I spoke to an experienced Cold War hand, who had skated through the collapse of the Soviet Union, and now occupied a high position in the nuclear bureaucracy of the increasingly assertive Russian state. In his corduroy suit, with his bushy eyebrows and heavy, sometimes glowering face, he looked like an apparatchik from central casting—and he acted like one, too. It was refreshing. He kept poking his finger at me, and accusing Americans of losing perspective over a nuclear Iran. He wanted to do nuclear business with Iran, in electric-power generation. He wanted to do nuclear business with all sorts of countries. He claimed that with one Russian submarine reactor (fueled by high-octane uranium) he could light up all sorts of cities. He meant with electricity. He proposed a scheme to mount such reactors on barges, to be pushed to places like Indonesia and then pulled away whenever the natives ran amok. This way, he said, he could keep his uranium from fueling native bombs. He did not deny the incentives for lesser nations to acquire nuclear devices, but he thought he could handle them, or perhaps he didn’t care. He said, “The Nuclear Non-Proliferation Treaty was the child of Russia and the United States. And this child was raised to fight against other countries, to resist the threat of proliferation. We’re talking about the 1970s. No one thought that proliferation could come from Arab countries, from Africa, from South America. The treaty was aimed at Western Germany, at Japan. It was aimed at dissuading the developed countries from acquiring nuclear weapons—and it worked because they accepted the U.S. and Soviet nuclear umbrellas.”
He was bullying history, but only by a bit. The Nuclear Non-Proliferation Treaty, or NPT, was an effort to preserve the exclusivity of a weapons club whose membership consisted originally of only five: Britain, China, France, the Soviet Union, and the United States. To other countries the treaty promised assistance with nuclear research and power generation in return for commitments to abstain from nuclear arms. It cannot be said to have “worked,” as my Russian friend claimed, but it did help to slow things down. More important, and completely independent of the NPT, were the Cold War alliances that, by offering retaliatory guarantees, eliminated the need for independent nuclear defense capabilities in those nations willing (or forced) to choose sides. But neither the Cold War alliances nor the NPT could counter the natural appeal of these devices—their fast-track, nation-equalizing, don’t-tread-on-me, flat-out-awesome destructive power.
In 1946 Robert Oppenheimer sketched the problem clearly. In an essay titled “The New Weapon,” he wrote: “Atomic explosives vastly increase the power of destruction per dollar spent, per man-hour invested; they profoundly upset the precarious balance between the effort necessary to destroy and the extent of the destruction.” Elaborating, he wrote,
None of these uncertainties can becloud the fact that it will cost enormously less to destroy a square mile with atomic weapons than with any weapons hitherto known to warfare. My own estimate is that the advent of such weapons will reduce the cost, certainly by more than a factor of ten, more probably by a factor of a hundred. In this respect only biological warfare would seem to offer competition for the evil that a dollar can do.
From his perch in Moscow my Russian friend had observed the effect of Oppenheimer’s truths. Continuing with his story of the NPT, he said, “Even as the U.S. and Russia offered our nuclear umbrellas, everyone understood that the weapons could never be used, because of retaliation. For us they were not wealth—they were a burden. At the same time, nuclear technology was becoming even cheaper, more efficient, and it became available to many countries. It became a useful tool especially for weak countries to satisfy their ambitions without much expense. There are no technical barriers, and no barriers to the flow of information, that can prevent it. Once a country has made the decision to become a nuclear-weapons power, it will become one regardless of any guarantees. You needn’t be rich. You needn’t be technically developed. You can be Pakistan, Libya, North Korea, Iran. You can be …” He searched for a country even more absurd in his estimation. He said, “You can be Hungary.” Then he said, “At some point this change occurred. The great powers were stuck with arsenals they could not use. And nuclear weapons became the weapons of the poor.”
It was a simplified view, but not entirely wrong. Certainly the argument can be made that only underdeveloped nations can now afford to use these weapons, not merely because the lives of their citizens seem to be expendable, but also because of the limitations of their nuclear arsenals, which mean that their warheads will incinerate just a few enemy cities, more or less locally, and will not likely frighten Russia and the United States into swapping strikes. The fate of the world is not at stake. Pakistan and India came close to a regional nuclear exchange in 2002, with little risk of igniting a global conflict. The core of that story, however, is that each antagonist had its own cities to protect—particularly its own capital—and each therefore had good reasons for backing down. This was a demonstration rather than a proof, but of special interest because it involved a country as backward as Pakistan. It seems to indicate as a general rule that even a stunted state is deterred by the threat of retaliation, because so long as its leaders have a government, an infrastructure, and indeed a delineated nation (not to mention their individual lives of luxury), they provide rich targets to be smashed and burned in answer to any first strike. At this point it appears that simple calculations of self-preservation should keep fingers off the triggers even in Pyongyang and Tehran. So we should be safe, relatively—but perhaps we are not.
The danger comes from a direction unforeseen in 1945, that this technology might now pass into the hands of the new stateless guerrillas, the jihadists, who offer none of the targets that have underlain our nuclear peace—no permanent infrastructure, no capital city, no country called home. The nuclear threat posed by the jihadists first surfaced in the chaos of post-Soviet Russia in the 1990s, and took full form after the fall of the World Trade Center. With so little to fear of nuclear retaliation, and having already panicked the United States into historic policy blunders, these are the rare people in a position to act.
If you were a terrorist and a bomb was your goal, how would you go about getting one? You could not bet on acquiring an existing weapon. These are held as critical national assets in fortified facilities guarded by elite troops, and they would be extremely difficult to get at, or to buy. Reports have suggested the contrary, particularly because of rumors about the penetration of organized crime into the Russian nuclear forces, and about portable satchel nukes, or “suitcase bombs,” which are said to have been built for the KGB in the late 1970s and 1980s, and then lost into the black market following the Soviet breakup. However, the existence of suitcase bombs has never been proved, and there has never been a single verified case, anywhere, of the theft of any sort of nuclear weapon. Thefts may nonetheless have occurred, but nuclear weapons require regular maintenance, and any still lingering on the market would likely have become duds. Conversely, because these time limitations are well known, the very lack of a terrorist nuclear strike thus far tends to indicate that nothing useful was ever stolen. Either way, even if the seller could provide a functioning device, nuclear weapons in Russia and other advanced states have sophisticated electronic locks that would defeat almost any attempt to trigger them. Of course you could look to countries where less rigorous safeguards are in place, but no government handles its nuclear arsenal loosely, or would dare to create the impression that it is using surrogates to fight its nuclear wars. Even the military leaders of Pakistan, who have repeatedly demonstrated their willingness to sell this technology, would balk at allowing a constructed device to escape—if only because of the certainty that this time they would be held to account. The same concerns would almost certainly restrain North Korea.
All this should give you pause long enough to take bearings. You would do well to distinguish between your needs and those of conventional proliferators. Fledgling nuclear-weapons states have little use for just one or two bombs. To assume a convincing posture of counterstrike and deterrence, or simply to exhibit nuclear muscle, they require a significant arsenal that can be renewed and improved and grown across time. This in turn requires that they build large-scale industrial facilities to produce warhead fuel, which cannot be purchased on the international black market in sufficient quantity to sustain a nuclear-weapons production line. Manufacturing high-quality fuel is the most difficult part of any nuclear program; the NPT is meant to interfere primarily at this stage. The construction of everything else is relatively easy.
You could hardly expect to set up the facilities to manufacture nuclear fuel. (Nor could you expect any state, whether Pakistan or North Korea, to risk helping you here, either.) But you would have no need to do so. There is plenty of weapons-grade fissile material in the world today, and more is being produced all the time. Surely you could steal or buy the quantity necessary for a single garage-made device.
You would now need to decide what kind of fuel to pursue. There are really only two choices—plutonium or highly enriched uranium. Plutonium is a man-made element produced by uranium reactors. There are several forms of it, including one purpose-made for bombs. Armies favor plutonium because it can be made to go critical in very small quantities, thereby lending itself to the miniaturization of weapons. Miniaturization has obvious attractions, but it requires a level of engineering sophistication that lies beyond the capabilities of a small terrorist team. And miniaturization is not that important for your purposes. You can operate well enough with a car-sized device locked into a shipping container or loaded into a private airplane behind a couple of dedicated pilots. Furthermore, plutonium has some negatives for an operation like yours. It is not suited for use in a basic cannon-type bomb, and demands instead the explosive symmetry of a Nagasaki-style implosion device. Building an implosion device would introduce complexities you would be better off avoiding, particularly without a place and the time to test the design. And plutonium is difficult to handle—sufficiently radioactive to require shielding, awkward to transport without setting off radiation detectors, and extremely dangerous even in minute quantities if it is breathed in, swallowed, or absorbed through a cut or open wound. There are plenty of people who would willingly die for the chance to nuke the United States, but within the limited pool of technicians who might join your effort, it would be impractical to expect so much. Plutonium might work as the pollutant spread by a dirty bomb, but for your project, plutonium is out.
The alternative is highly enriched uranium, or HEU, the variant of natural uranium that has been refined to contain artificially dense concentrations of the fissionable isotope U‑235. Operationally it is wonderful material—the perfect fuel for a garage-made bomb. During processing, uranium takes the form of an invisible gas, a liquid, a powder, and finally a dull grey metal. It has approximately the toxicity of lead, and would sicken shop workers who happened to swallow traces of it or breathe in its dust, but otherwise it is not immediately dangerous, and indeed is so mildly radioactive that it can be picked up with bare hands and, when lightly shielded, taken past many radiation monitors without setting off alarms. As one physicist in Washington suggested to me, in small masses HEU is so benign that you could sleep with it under your pillow. He warned me, however, that you could not just pile it up in your bed, or anywhere else, because the atoms of U‑235 occasionally split apart spontaneously, and in doing so fire off neutrons, which within a sufficient mass of material could split enough other atoms to cause a chain reaction. Such a reaction would not amount to a military-style nuclear explosion, but it could certainly take out a few city blocks.
I asked the physicist if he wasn’t concerned about giving information to terrorists. He summoned his patience visibly and said, to paraphrase it, This is Boy Scout Nuclear Merit Badge stuff. We continued our discussion. He said that the critical mass of uranium is inversely proportional to the level of enrichment. At the low end of HEU, which is considered to be 20 percent enrichment, nearly a ton would have to be combined before a stockpile could spontaneously ignite. At the high end, which is the “weapons grade” enrichment of 90 percent or greater, about 100 pounds could do the trick. I mentioned that at whatever level of enrichment, the HEU that a terrorist could acquire would by definition be made of units each consisting of less than a critical mass. I asked the physicist to imagine that a terrorist had acquired two bricks of weapons-grade HEU, each weighing fifty pounds: how far apart would he have to keep them? He said that a yard would be enough. I had arrived in Washington from remote mountains along the Turkish border with Iran, where every night hundreds of pack horses are led across the line by Kurdish smugglers, carrying cheap fuel for Turkish cars and opium for the European heroin market. This is the Silk Road revived, and it is one of the prime potential routes for the movement of stolen uranium. With this in mind, I told the physicist I assumed from his measure that the two bricks could be slung on either side of a saddle.
He said, “One on each side should be all right …” He hesitated. “But what is the moderating effect of a horse?”
I had no idea. He said, “Look, if someone’s smart enough to have snuck in and gotten ahold of these two ingots of metal, he’ll be smart enough to negotiate for a second horse.”