Eighty years ago – on Aug. 6 and 9, 1945 – the U.S. military dropped atomic bombs on Hiroshima and Nagasaki, Japan, thrusting humanity into a terrifying new age. In mere moments, tens of thousands of people perished in deaths whose descriptions often defy comprehension.
The blasts, fires and lingering radiation effects caused such tragedies that even today no one knows exactly how many people died. Estimates place the death toll at up to 140,000 in Hiroshima and over 70,000 in Nagasaki, but the true human costs may never be fully known.
The moral shock of the U.S. attacks reverberated far beyond Japan, searing itself into the conscience of global leaders and the public. It sparked a movement I and others continue to study: the efforts of the international community to ensure that such horrors are never repeated.
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Racing toward the brink
The memories of Hiroshima and Nagasaki cast a long shadow over global efforts to contain nuclear arms. The 1968 Treaty on the Non-Proliferation of Nuclear Weapons, more commonly known as the Nuclear Nonproliferation Treaty, was a powerful, if imperfect, effort to prevent future nuclear catastrophe. Its creation reflected not just morality, but also the practical fears and self-interests of nations.
As the years passed, views of the bombings as justified acts began to shift. Harrowing firsthand accounts from Hibakusha – the survivors – reached wide audiences. One survivor, Setsuko Thurlow, described the sight of other victims:
“It was like a procession of ghosts. I say ‘ghosts’ because they simply did not look like human beings. Their hair was rising upwards, and they were covered with blood and dirt, and they were burned and blackened and swollen. Their skin and flesh were hanging, and parts of the bodies were missing. Some were carrying their own eyeballs.”
Nuclear dangers increased further with the advent of hydrogen bombs, or thermonuclear weapons, capable of destruction far greater than the atomic bombs dropped on Hiroshima and Nagasaki. What had once seemed a decisive end to a global war now looked like the onset of an era wherein no city or civilization would truly be safe.
These shifting perceptions shaped how nations viewed the nuclear age. In the decades following World War II, nuclear technology rapidly spread. By the early 1960s, the United States and the Soviet Union aimed thousands of nuclear warheads at one another.
Meanwhile, there were concerns that countries in East Asia, Europe and the Middle East would acquire the bomb. U.S. President John F. Kennedy even warned that “15 or 20 or 25 nations” might be able to develop nuclear weapons during the 1970s, resulting in the “greatest possible danger” to humanity – the prospect of its extinction. This warning, like much of the early nonproliferation rhetoric, drew its urgency from the legacies of Hiroshima and Nagasaki.
Perhaps the starkest indication of the gravity of the stakes emerged during the Cuban missile crisis of October 1962. For 13 days, the world teetered on the edge of nuclear annihilation until the Soviet Union withdrew its missiles from Cuba in exchange for the secret withdrawal of U.S. missiles from Turkey. During those long days, U.S. and Soviet leaders – and external observers – witnessed how quickly the risks of global destruction could escalate.
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Crafting the grand bargain
In the wake of such “close calls” – moments where nuclear war was narrowly averted due to individual judgment or sheer luck – diplomacy accelerated.
Negotiations on a treaty to control nuclear proliferation continued at meetings of the Eighteen Nation Disarmament Committee in Geneva from 1965 to 1968. While the enduring horrors of Hiroshima and Nagasaki helped to drive the momentum, national interests largely shaped the talks.
There were three groups of negotiating parties. The United States was joined by its NATO allies Britain, Canada, Italy and France – which only observed. The Soviet Union led a communist bloc containing Bulgaria, Czechoslovakia, Poland and Romania. And there were nonaligned countries: Brazil; Burma, now known as Myanmar; Ethiopia; India; Mexico; Nigeria; Sweden, which only joined NATO in 2024; and the United Arab Republic, now known as Egypt.
For the superpowers, a treaty to limit the spread of the bomb was as much a strategic opportunity as a moral imperative.
Keeping the so-called “nuclear club” small would not only stabilize international tensions, but it would also cement Washington’s and Moscow’s global leadership and prestige.
U.S. leaders and their Soviet counterparts therefore sought to promote nonproliferation abroad. Perhaps just as important as ensuring nuclear forbearance among their adversaries was preventing a cascade of nuclear proliferation among allies that could embolden their friends and spiral out of control.
Standing apart from these Cold War blocs were the nonaligned countries. Many of them approached the atomic age through a humanitarian and moral lens. They demanded meaningful action toward nuclear disarmament to ensure that no other city would suffer the tragic fate of Hiroshima and Nagasaki.
The nonaligned countries refused to accept a two-tiered treaty merely codifying inequality between nuclear “haves” and “have-nots.” In exchange for agreeing to forgo the bomb, they demanded two crucial commitments that shaped the resulting treaty into what historians often describe as a “grand bargain.”
The nonaligned countries agreed in the treaty to permit the era’s existing nuclear powers – Britain, China, France, the Soviet Union (later Russia) and the United States – to temporarily maintain their arsenals while committing to future disarmament. But in exchange, they were promised peaceful nuclear technology for energy, medicine and development. And to reduce the risks of anyone turning peaceful nuclear materials into weapons, the treaty empowered the International Atomic Energy Agency to conduct inspections around the world.
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Legacies and limits
The treaty entered into force in 1970 and with, 191 member nations, is today among the world’s most universal accords. Yet, from the outset, its provisions faced limits. Nuclear-armed India, Israel and Pakistan have always rejected the treaty, and North Korea later withdrew to develop its own nuclear weapons.
In response to evolving challenges, such as the discovery of Iraq’s clandestine nuclear weapons program in the early 1990s, International Atomic Energy Agency safeguard efforts grew more stringent. Many countries agreed to accept nuclear facility inspections on shorter notice and involving more intrusive tools as part of the initiative to detect and deter the development of the world’s most powerful weapons. And the countries of the world extended the treaty indefinitely in 1995, reaffirming their commitment to nonproliferation.
The treaty represents a complex compromise between morality and pragmatism, between the painful memories of Hiroshima and Nagasaki and hard-edged geopolitics. Despite its many imperfections and its de facto promotion of nuclear inequality, the treaty is credited with limiting nuclear proliferation to just nine countries today. It has done so through civilian nuclear energy incentives and inspections that give countries confidence that their rivals are not building the bomb. Countries also put pressure on each other to obey the rules, such as when the international community condemned, sanctioned and isolated North Korea after it withdrew from the treaty and tested a nuclear weapon.
But the treaty continues to face serious challenges. Critics argue that its disarmament provisions remain vague and unfulfilled, with some scholars contending that nonnuclear countries should exit the treaty to encourage the great powers to disarm. Nuclear-armed countries continue to modernize – and in some cases, expand – their arsenals, eroding trust in the grand bargain.
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The behavior of individual countries also points to strains on the treaty. Russia’s persistent nuclear threats during its war on Ukraine show how deeply possessors may still rely on these weapons as tools of coercive foreign policy. North Korea continues to wield its nuclear arsenal in ways that undermine international security. Iran might consider proliferation to deter future Israeli and U.S. strikes on its nuclear facilities.
Still, I would argue that declaring the treaty to be dead is simply premature. Critics have predicted its demise since the treaty’s inception in 1968. While many countries have growing frustrations with the existing system of nonproliferation, most of them still see more benefit in staying than walking away from the treaty.
The treaty may be embattled, but it remains intact. Worryingly, the world today appears far removed from the vision of avoiding nuclear catastrophe that Hiroshima and Nagasaki helped awaken. As nuclear dangers intensify and disarmament stalls, moral clarity risks fading into ritual remembrance.
I believe that for the sake of humanity’s future, the tragedies of the atomic bombings must remain a stark and unmistakable warning, not a precedent. Ultimately, the Nuclear Nonproliferation Treaty’s continued relevance depends on whether nations still believe that shared security begins with shared restraint.