During the Manhattan Project, physicist Enrico Fermi was asked about the chance that the first nuclear test might ignite the atmosphere. With dry humour, he replied: “Well, I would say two or three per cent.” The audience laughed nervously, revealing the surreal mix of humour and dread that surrounded the birth of nuclear weapons. This scientific uncertainty set the tone for how nuclear power was perceived—not merely as a technical achievement, but as a force that could threaten existence itself.Winston Churchill, Britain’s wartime Prime Minister, was briefed about the atomic bomb after the war. He reportedly remarked: “This is the Second Coming in Wrath.” His words reflected both awe and fear at the destructive power unleashed. From the laboratory to the corridors of power, nuclear weapons were quickly recognised as instruments that transcended ordinary warfare, shaping political imagination and global strategy.After Hiroshima, many ordinary citizens in the United States expressed mixed feelings. One woman in New York said: “Thank God the war is over, but I can’t help wondering what kind of world we’ve entered.” Her words captured the paradox of victory shadowed by dread. Such public voices remind us that nuclear weapons were not only a matter of politics and science, but also a source of anxiety for everyday people who sensed the dawn of a new and uncertain era.In post-war Japan, survivors recalled children asking why the “pikadon” (flash-bang) had happened. The innocent phrasing became a poignant anecdote of how ordinary people tried to make sense of devastation. This final perspective brings us to the human core of the nuclear story—where innocence, trauma, and memory converge—preparing us to examine the broader possibilities of nuclear use in war, diplomacy, and deterrence.The anecdotes surrounding the atomic bomb—whether Fermi’s dry humour, Churchill’s solemn awe, or the innocent questions of Japanese children—reveal more than mere reactions. They highlight the profound uncertainty and moral unease that accompanied the dawn of nuclear weapons. Such stories serve as a bridge, reminding us that behind every technical achievement lies a human dimension of fear, wonder, and responsibility.From these moments of public and political reflection, it becomes clear that the bomb was never simply a military tool. Instead, it was perceived as a force capable of reshaping the very fabric of international relations and human existence. This perception naturally leads us to consider the possible uses of nuclear weapons—not only in war, but also in diplomacy, deterrence, and the shaping of global order.Thus, the anecdotes act as entry points into a broader discussion. They show how humour, dread, and curiosity converged in the face of unprecedented power, and they prepare us to examine the practical, strategic, and ethical possibilities of nuclear deployment in the decades that followed.THE NUCLEAR THRESHOLDHistory, Proliferation, and the Prospect of Use in the Twenty-First CenturyI. Introduction: The Shadow That Has Never LiftedOn 6 August 1945, at 8:15 in the morning, a single American aircraft released a device above the Japanese city of Hiroshima that killed between 70,000 and 80,000 people in an instant and would claim, through radiation and injury, perhaps 140,000 lives by the end of that year. Three days later, a second bomb fell on Nagasaki. In those two moments, humanity crossed a threshold from which it has never returned. Nuclear weapons—devices capable of obliterating entire cities with the destructive energy of tens of thousands of tonnes of conventional explosive—became a permanent feature of the international order.More than eight decades have elapsed since Hiroshima and Nagasaki. In that span, the world has been fortunate: no nuclear weapon has been fired in anger. Yet this fortunate record conceals a history of extraordinary danger—of crises that came perilously close to catastrophe, of miscalculations narrowly averted, of command-and-control failures that could have ended civilisation. And as the twenty-first century deepens, the conditions that sustained the long nuclear peace are eroding. Geopolitical rivalries are sharpening, arms control architecture is collapsing, and the circle of nuclear-armed states has widened.This essay proceeds in two parts. The first surveys the history of nuclear weapons: from the Manhattan Project and the bombings of Japan, through the Cold War arms race, to the present configuration of nuclear-armed states and their arsenals. The second part undertakes an analytical assessment of the scenarios under which nuclear weapons might be used—by which actors, under which circumstances, and with what likely consequences. The purpose is not alarmism but clarity: to understand the nuclear question with the seriousness it demands.PART ONE: THE HISTORY OF NUCLEAR WEAPONSII. Origins: Physics, Politics, and the Manhattan ProjectThe intellectual foundations of nuclear weapons were laid not by soldiers or statesmen but by physicists—men and women working at the frontier of the understanding of matter itself. In 1905, Albert Einstein published his special theory of relativity, which contained the famous equation E = mc², establishing that mass and energy are interconvertible at an exchange rate governed by the square of the speed of light. The energy locked within even a small quantity of matter was, by this reckoning, almost incomprehensibly vast.The practical path to exploiting that energy began to open in the 1930s. In 1932, James Chadwick at Cambridge discovered the neutron. In 1938, the German chemists Otto Hahn and Fritz Strassmann, working in Berlin, demonstrated nuclear fission: the splitting of a uranium nucleus by a slow neutron, releasing energy and producing further neutrons capable of splitting additional nuclei. The physicist Lise Meitner—who had collaborated with Hahn but been forced to flee Nazi Germany as a Jewish woman—provided the theoretical interpretation. The chain reaction, the conceptual heart of the atomic bomb, was now imaginable.What turned this scientific possibility into a military programme was the political catastrophe of the Second World War and, above all, the fear that Nazi Germany might develop the weapon first. In August 1939, Einstein and the Hungarian physicist Leó Szilárd wrote to President Franklin D. Roosevelt, warning that Germany might be developing nuclear weapons and urging the United States to pursue its own programme. Roosevelt authorised preliminary research.The Manhattan Project—the vast, secret American industrial and scientific effort to build the bomb—formally came into being in 1942 under the direction of General Leslie Groves, with the physicist J. Robert Oppenheimer as scientific director. At its peak, it employed more than 130,000 people across sites including Los Alamos in New Mexico, Oak Ridge in Tennessee, and Hanford in Washington State. It consumed some $2 billion (equivalent to roughly $30 billion today) and drew upon the greatest concentration of scientific talent in history, including refugees from fascist Europe: Enrico Fermi, Hans Bethe, Edward Teller, and many others.On 16 July 1945, at a test site in the New Mexico desert known as Trinity, the first nuclear device — nicknamed 'the Gadget'—was detonated. The yield was approximately 21 kilotons of TNT equivalent. Watching the explosion, Oppenheimer reportedly recalled a line from the Hindu scripture Bhagavad Gita: 'Now I am become Death, the destroyer of worlds.' By then, Germany had already surrendered. The weapon had been built to fight one enemy; it would be used against another.III. Hiroshima and Nagasaki: The First and Only Use in WarThe decision to deploy atomic bombs against Japan remains one of the most debated in modern history. President Harry S. Truman, who had assumed the presidency upon Roosevelt's death in April 1945, was told of the Manhattan Project only after taking office. He and his advisers faced a stark military situation: Japan showed no signs of surrender despite the devastation visited upon its cities by conventional bombing, and American military planners projected that an invasion of the Japanese home islands could cost hundreds of thousands of American and millions of Japanese lives.On 6 August 1945, the B-29 bomber Enola Gay, piloted by Colonel Paul Tibbets, dropped a uranium-based bomb—'Little Boy'—on Hiroshima, the headquarters of Japan's Second Army. The explosion, at a height of roughly 600 metres, released energy equivalent to approximately 15 kilotons of TNT. The temperature at the hypocentre reached an estimated 4,000 degrees Celsius. Buildings within a kilometre were obliterated. Fires raged across the city. Between 70,000 and 80,000 people died immediately; radiation sickness, burns, and injuries would bring the total to perhaps 140,000 by December 1945.On 9 August, a plutonium bomb—' Fat Man'—was dropped on Nagasaki, the second-choice target after the primary target of Kokura was obscured by cloud. The Nagasaki bomb was more powerful—approximately 21 kilotons—but the city's hilly topography confined the blast somewhat, and immediate deaths are estimated at between 40,000 and 50,000, rising to approximately 80,000 by year's end. On 15 August 1945, Emperor Hirohito announced Japan's surrender.The moral and strategic debates provoked by these bombings have never been fully resolved. Defenders argue that the bombs ended the war quickly, prevented a catastrophic invasion, and ultimately saved more lives than they destroyed. Critics contend that Japan was already on the verge of surrender, that the bombings were directed at civilian populations in contravention of the laws of war, and that they were in part an act of geopolitical signalling directed at the Soviet Union. What is certain is that Hiroshima and Nagasaki established the parameters of nuclear horror—parameters that have shadowed international politics ever since.IV. The Cold War Arms Race: Deterrence, Proliferation, and Near-MissesThe American monopoly on nuclear weapons lasted barely four years. The Soviet Union, drawing upon its own programme and upon intelligence obtained partly through espionage, detonated its first atomic bomb in August 1949. The United Kingdom followed in 1952, France in 1960, and China in 1964. The nuclear club was expanding even as the Cold War between the United States and the Soviet Union was shaping every dimension of international politics.The development of thermonuclear weapons—hydrogen bombs, which use a fission device to trigger a vastly more powerful fusion reaction—raised the destructive potential to a qualitatively different level. The United States detonated its first thermonuclear device in 1952; the Soviet Union followed in 1953. By the mid-1950s, both superpowers possessed weapons thousands of times more destructive than those dropped on Japan. A single large thermonuclear warhead could, in principle, destroy an entire metropolitan area.The doctrine of mutual assured destruction (MAD) emerged as the operative logic of nuclear deterrence. The reasoning was grim but coherent: if each superpower maintained a secure second-strike capability—the ability to absorb a nuclear first strike and still retaliate with devastating effect—neither would rationally initiate a nuclear exchange. The weapons, paradoxically, became useful precisely because they were intended never to be used. Stability rested upon the credibility of mutual annihilation.Yet the Cold War nuclear peace was not placid. Its most dangerous moment came in October 1962, when American reconnaissance aircraft photographed Soviet missile installations under construction in Cuba. The thirteen-day Cuban Missile Crisis brought the world closer to nuclear war than at any other moment in the nuclear age. President John F. Kennedy and Premier Nikita Khrushchev negotiated a resolution—Soviet missiles would be withdrawn from Cuba in exchange for an American pledge not to invade the island and a secret agreement to remove American missiles from Turkey—but the outcome was far from foreordained. Subsequent research has revealed that Soviet submarines in the area were carrying nuclear-armed torpedoes, and that at least one Soviet submarine commander came close to authorising their use against American vessels.Less well known but comparably dangerous was the Able Archer 83 exercise of November 1983, in which NATO simulated the transition to nuclear warfare with a realism that convinced Soviet intelligence that an actual Western nuclear first strike might be imminent. Soviet nuclear forces were placed on heightened alert. Only later did Western leaders learn how close the world had come to a catastrophic misunderstanding.Arms control emerged as the principal institutional mechanism for managing nuclear danger. The Limited Test Ban Treaty (1963) prohibited nuclear tests in the atmosphere, outer space, and underwater. The Nuclear Non-Proliferation Treaty (NPT, 1968) sought to prevent the spread of nuclear weapons beyond the five recognised nuclear states while committing those states to eventual disarmament. The SALT I and II agreements, and later START I and II, placed limits on strategic nuclear arsenals. The Intermediate-Range Nuclear Forces (INF) Treaty of 1987, signed by Reagan and Gorbachev, eliminated an entire category of nuclear weapons from Europe.V. After the Cold War: New Proliferators and Eroding ArchitectureThe end of the Cold War did not end the nuclear danger; it transformed it. The Soviet arsenal was divided among four successor states — Russia, Ukraine, Belarus, and Kazakhstan—and the latter three ultimately relinquished their weapons to Russia under the Budapest Memorandum of 1994, in which Ukraine received security assurances (though not formal guarantees) from Russia, the United States, and the United Kingdom. That undertaking's subsequent breach, when Russia annexed Crimea in 2014 and invaded Ukraine fully in 2022, has cast a long shadow over non-proliferation diplomacy.Three states acquired nuclear weapons outside the NPT framework. India and Pakistan, which had fought three conventional wars, both conducted nuclear tests in 1998. Both now possess arsenals estimated at 160 to 170 warheads each. Their mutual deterrence operates in a peculiarly dangerous environment: the two countries share a contested border, have fought multiple limited wars, experience periodic crises precipitated by cross-border terrorism, and have shorter warning times for ballistic missiles than the Cold War superpowers ever did.Israel has maintained a policy of nuclear ambiguity—neither confirming nor denying possession of nuclear weapons—since at least the 1960s, when it is generally believed to have acquired the capability. Estimates of Israel's arsenal vary from approximately 80 to 400 warheads. North Korea, after years of developing its programme under international sanctions, conducted its first nuclear test in 2006 and has since refined its weapons to include thermonuclear devices and delivery systems capable, in principle, of reaching the continental United States.Meanwhile, the arms control architecture constructed during the Cold War has been significantly dismantled. The United States withdrew from the Anti-Ballistic Missile Treaty in 2002, enabling the development of missile defence systems that Russia regards as threatening to its deterrent. The INF Treaty, which had eliminated ground-launched intermediate-range missiles, was abandoned in 2019 following mutual accusations of non-compliance. The New START Treaty—the last remaining bilateral strategic arms control agreement between the United States and Russia—was suspended by Russia in 2023 in the context of the war in Ukraine. Negotiations for its successor have not been initiated.The global nuclear stockpile at its peak, in the mid-1980s, exceeded 70,000 warheads. It has since been reduced dramatically, to approximately 12,100 warheads as of early 2026, of which roughly 9,600 are in the military stockpiles of the nine nuclear-armed states and approximately 3,900 are deployed—that is, placed on missiles or at bomber bases. The reductions are real, but the remaining arsenal is still more than sufficient to end industrial civilisation.PART TWO: THE PROSPECT OF USE — AN ANALYTICAL ASSESSMENTVI. The Nine Nuclear-Armed States: A SurveyAny analysis of nuclear use must begin with a survey of the nine states that possess nuclear weapons and the strategic doctrines that govern them.The United StatesThe United States possesses approximately 5,550 warheads, of which roughly 1,700 are deployed on a triad of land-based intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and nuclear-capable aircraft. American nuclear doctrine is governed by the Nuclear Posture Review, most recently updated in 2022, which contemplates nuclear use in extreme circumstances, including not only nuclear attack but also non-nuclear attacks of strategic magnitude against the United States, its allies, or partners. The United States has historically maintained a 'no first use' ambiguity—declining to rule out first use—and remains committed to extended deterrence for NATO allies, Japan, and South Korea.
\RussiaRussia possesses approximately 6,200 warheads—the world's largest arsenal—including a significant number of non-strategic (tactical) nuclear weapons for which no binding international limits exist. Russian nuclear doctrine, updated in 2020, explicitly contemplates nuclear use in response to conventional attacks that threaten the 'existence of the state,' a formulation that has taken on acute significance in the context of the war in Ukraine. Since 2022, Russian officials—including President Vladimir Putin—have made repeated public references to nuclear weapons, raising Western concerns about Russian willingness to use them coercively.
ChinaChina has historically maintained a relatively small arsenal under a declared 'no first use' policy, but is engaged in a rapid and substantial build-up. Estimates suggest China now possesses approximately 500 warheads and is projected to reach 1,000 by 2030 and 1,500 by 2035. China is also constructing hundreds of new ICBM silos. This expansion is altering the strategic calculus in the Indo-Pacific and complicating any future US-Russia bilateral arms control framework, since China would need to be included in any comprehensive regime.
The United Kingdom and FranceBoth Britain and France maintain relatively small arsenals—approximately 225 and 290 warheads respectively—consisting primarily of submarine-launched missiles. Both are committed to NATO's nuclear sharing arrangements. Their doctrines emphasise deterrence of existential threats and are calibrated to the minimum credible deterrent rather than to war-fighting.
India and PakistanIndia and Pakistan each possess approximately 160 to 170 warheads. India's doctrine is guided by 'no first use' and 'credible minimum deterrence,' though analysts have debated whether India's actual posture is consistent with those commitments. Pakistan explicitly rejects no first use, maintaining nuclear weapons as an equaliser against India's conventional superiority. The possibility of Pakistani use in response to a losing conventional battle is a particular concern among strategists.
IsraelIsrael's nuclear arsenal remains officially unacknowledged but is widely estimated at between 80 and 400 warheads. Israeli doctrine—to the extent it can be inferred—appears to contemplate nuclear weapons as a last resort against existential threats, an approach sometimes called the 'Samson Option.' The volatile state of the Middle East, including Iran's nuclear ambitions and the ongoing Israeli-Palestinian and Israeli-Iranian conflicts, makes Israel's situation one of the most strategically fraught in the world.
North KoreaNorth Korea is estimated to have between 40 and 50 nuclear warheads, with fissile material for perhaps 80 to 90. Its delivery systems include ICBMs potentially capable of reaching the United States. Kim Jong-un's regime appears to view nuclear weapons not only as a deterrent but as a tool of coercion and regime survival. Doctrine is opaque, but North Korea has codified into law the pre-emptive use of nuclear weapons in certain circumstances, including threats to the leadership.VII. Scenarios for Nuclear Use: A TypologyThe question of where and how nuclear weapons might actually be used is best approached through a systematic consideration of the scenarios most frequently analysed by strategic thinkers. These scenarios differ along several dimensions: the scale of use (tactical vs. strategic), the actors involved, the degree of deliberateness, and the role of escalation dynamics.Scenario A: Russia and the War in UkraineThe ongoing Russo-Ukrainian War, which began with Russia's full-scale invasion in February 2022, has introduced the most concrete nuclear risk the world has faced since the Cold War. Russia's nuclear signalling has been unprecedented in its frequency and explicitness. The scenario most commonly discussed is the use of a tactical nuclear weapon—a lower-yield battlefield device—either against Ukrainian forces, as a demonstration strike on Ukrainian territory, or against the supply lines or territory of a NATO state providing military assistance.The rationale for such use would likely be military reversal combined with the calculation that NATO would not respond in kind, fearing escalation. The risks of this path are, however, enormous. A nuclear strike on Ukraine would likely trigger severe conventional and economic retaliation by the Western alliance, could prompt other nuclear states to reconsider their own doctrines, and would demolish the nuclear taboo that has governed international relations since 1945. Precisely this uncertainty—about how the West would respond—has thus far appeared to restrain Russian decision-making, even in moments of acute military stress.Scenario B: South Asia—India and PakistanThe India-Pakistan nuclear dyad represents what many strategists regard as the most dangerous nuclear situation in the world. Both countries have relatively small arsenals on high alert, short missile flight times of approximately five minutes between capitals, and a history of crises that have come close to conventional conflict. Scenarios for nuclear use typically involve a major terrorist attack on India attributed to Pakistani-based groups—as occurred in 2001 and 2008—followed by an Indian conventional military response that crosses Pakistani red lines, at which point Pakistan faces the choice of conventional defeat or nuclear use.A regional nuclear exchange between India and Pakistan could kill millions directly. Studies have suggested that even a limited exchange—100 Hiroshima-scale bombs—could inject sufficient soot and smoke into the stratosphere to reduce global temperatures by 1 to 2 degrees Celsius for a decade, disrupting agriculture globally and potentially causing a billion additional deaths from famine. This 'nuclear winter' effect makes a South Asian nuclear exchange a global catastrophe even for states far removed from the conflict.Scenario C: North Korea and the Korean PeninsulaNorth Korea's nuclear weapons serve multiple purposes for Pyongyang: regime survival through deterrence, coercive leverage over South Korea and the United States, and potentially a tool of last resort in any conflict that threatens the regime's existence. The most plausible scenarios for use involve either a pre-emptive North Korean strike in anticipation of a regime-change military operation, or use in the final stages of a losing conventional conflict. A North Korean nuclear strike against South Korean cities or American military bases in the region could kill hundreds of thousands immediately and would inevitably trigger an overwhelming American conventional and potentially nuclear response.
Scenario D: Middle East—Israel and IranIran's nuclear programme has been a central preoccupation of Israeli strategic planning for two decades. Israel has repeatedly signalled that it would take military action to prevent Iran from acquiring a nuclear weapon. Were Iran to approach the nuclear threshold—or cross it—Israel might conduct pre-emptive strikes against Iranian nuclear facilities. The risk of nuclear use in this context involves not Israel initiating nuclear warfare but rather the escalatory dynamics that could follow Israeli conventional strikes on Iran, Iranian retaliation against Israel, and Israel's potential use of nuclear weapons if it faced an existential military threat.The situation is further complicated by the regional dimension: Iran's nuclear capability, if achieved, could trigger a cascade of proliferation among neighbouring states—Saudi Arabia, Turkey, Egypt, and others—that might seek their own nuclear deterrents. A multi-polar nuclear Middle East would be extraordinarily difficult to manage.Scenario E: Accident, Miscalculation, or Unauthorised UseHistory provides numerous examples of near-misses stemming not from deliberate decision but from technical malfunction, intelligence failure, or command failure. In 1983, the Soviet early-warning satellite system gave a false indication of an American missile launch; Stanislav Petrov, the duty officer, correctly judged it to be a malfunction and did not report it as an attack. In 1995, Russia briefly prepared to launch missiles after detecting what turned out to be a Norwegian scientific rocket that had been mistaken for a US submarine-launched ballistic missile.As nuclear arsenals age, as cyber capabilities increasingly threaten command-and-control systems, and as warning times shorten with the proliferation of hypersonic missiles, the risk of accident or miscalculation increases. The states most vulnerable to these failures are those with the least sophisticated command-and-control arrangements—Pakistan, North Korea, and, in a crisis, any state operating under extreme stress.Scenario F: Non-State Actors and Radiological TerrorismThe acquisition of nuclear weapons by terrorist organisations remains one of the most feared scenarios in counter-proliferation policy, though arguably the least likely given the technical and logistical barriers involved. More plausible is radiological terrorism—the construction of a 'dirty bomb,' combining conventional explosives with radioactive material that could contaminate an urban area and cause mass panic, enormous economic disruption, and political crisis, even if casualties from radiation were relatively limited. The international community has worked to secure radioactive materials globally, but vulnerabilities remain, particularly in states with weak governance.VIII. The Erosion of the Nuclear TabooOne of the most consequential features of the post-1945 nuclear order has been the nuclear taboo: the powerful political and moral norm against the use of nuclear weapons, reinforced by the memory of Hiroshima and Nagasaki, by the development of international humanitarian law, and by the repeated choices of nuclear-armed states not to use their weapons even when they might have had military incentives to do so. The United States did not use nuclear weapons in Korea, in Vietnam, or in its other post-1945 conflicts. The Soviet Union did not use them in Afghanistan. China has never used its weapons offensively.That taboo, however, has shown signs of weakening. Russian political and military discourse has normalised nuclear signalling to a degree without precedent since the Cold War. North Korea has codified pre-emptive use in law. Some voices in strategic debates—particularly in South Asia and the Middle East—have questioned whether the taboo is truly universal or merely a reflection of a particular balance of power. As the generation that lived through Hiroshima and Nagasaki passes from the scene, the visceral memory that has sustained the taboo will fade.The collapse of arms control further erodes the institutional framework that has sustained restraint. When the NPT was concluded in 1968, it rested on a bargain: non-nuclear states would forgo weapons in exchange for the nuclear states' commitment to disarm. That commitment has never been fulfilled. The frustration of non-nuclear states with the double standard—in which the nuclear powers insist on their own deterrents while prohibiting others from acquiring them—has fuelled support for the Treaty on the Prohibition of Nuclear Weapons (TPNW, 2021), which none of the nuclear-armed states has signed.IX. Consequences: The Scale of CatastropheAny honest analysis of nuclear use must confront the scale of its potential consequences. A single modern thermonuclear warhead detonated over a major city would release energy of approximately one megaton—equivalent to 1,000 Hiroshima bombs. The immediate blast, heat, and radiation would kill hundreds of thousands. The ensuing firestorm, if the weapon were detonated over a dense urban area, would kill hundreds of thousands more.A large-scale nuclear exchange between the United States and Russia—involving even a fraction of their arsenals—would have global consequences. The most comprehensive scientific modelling suggests that such an exchange could inject five to 150 million tonnes of soot into the stratosphere, blocking sunlight, reducing global temperatures by up to 10 degrees Celsius for several years, and devastating global agriculture. Estimates of global famine deaths in such a scenario range from hundreds of millions to five billion. The extinction of industrial civilisation—and possibly of the human species—cannot be excluded.Even a 'limited' regional exchange, as noted above, would have global agricultural and humanitarian consequences far beyond the region affected. There is, in the nuclear domain, no clean or localised catastrophe. Every nuclear war is, potentially, a world war by other means.X. Conclusion: Living Under the Nuclear ShadowThe history of nuclear weapons is a history of astonishing scientific achievement, of catastrophic violence, and of a decades-long, imperfect, but partially successful effort to manage an unprecedented danger. The bombings of Hiroshima and Nagasaki demonstrated what these weapons do to human beings. The Cold War demonstrated that great powers can, under certain conditions, be restrained by mutual deterrence. The period since has demonstrated that those conditions are not permanent.The twenty-first century presents a more complex nuclear landscape than the Cold War: more actors, more contested regions, weakening arms control, and a global political culture in which the memory of Hiroshima is fading. The scenarios assessed here—Russia and Ukraine, South Asia, the Korean Peninsula, the Middle East, accident and miscalculation, radiological terrorism—are not remote or theoretical. Each represents a real combination of actors, interests, capabilities, and dynamics that could, under conditions of stress, produce nuclear use.What sustains the hope that nuclear use can continue to be avoided? Several things: the continued functioning of deterrence, however imperfect; the residual strength of the nuclear taboo; the interests of nuclear states in avoiding wars that would destroy what they seek to protect; the work of arms control diplomats and non-proliferation institutions; and, not least, the informed engagement of citizens and policymakers with the reality of nuclear danger.That engagement begins with knowledge—of what these weapons are, of how they came to exist, of who possesses them and why, and of how they might be used. It is in that spirit that this essay has been written. The nuclear shadow has never lifted. The question is whether humanity will have the wisdom to ensure it never falls.
[Part 19]
