If you have had the chance to see the poster or leaflet on the “World’s Nuclear Warhead Data," this digital guide will deepen your understanding of the issues to do with nuclear weapons. We present this guide in a Q&A format to answer frequently asked questions. We especially hope that the guide will be used in educational settings such as schools.
The poster illustrating the “World’s Nuclear Warhead Data" was first produced in 2013 by the PCU Nagasaki Council for Nuclear Weapons Abolition (PCU-NC), a collaborative council for nuclear weapons abolition formed by Nagasaki Prefecture, Nagasaki City, and Nagasaki University—together with the Research Center for Nuclear Weapons Abolition, Nagasaki University (RECNA). The aim of the poster is to clearly illustrate the current state of “a world with nuclear weapons.” The poster is updated with the latest information and released each June to support the peace education efforts leading up to the anniversaries of the atomic bombings of Hiroshima and Nagasaki in August. The poster underwent a major design renewal in 2024.
A comprehensive database serving as the basis for the poster is available on RECNA’s website. Please visit the site for more information.
Nine countries possess nuclear warheads: Russia, the United States, China, France, the United Kingdom, India, Pakistan, Israel, and North Korea. As of June 2024, the total number of nuclear warheads held by these nine countries is estimated at 12,120. Of those, the number that are “deployable” stands at 9,583.
A nuclear warhead is the component of a nuclear weapon that causes an explosion. A nuclear warhead combined with a missile or another delivery system to carry it is called a “nuclear weapon."
Nuclear warheads can be categorized into the following three kinds based on their status. The sum of these three kinds constitutes the “total number.”
On the other hand, the “number of deployable nuclear warheads" is the “total number of warheads” minus the “number of retired or to-be-dismantled warheads.” Put more simply, this is the number of warheads that can actually be used. This number gives us a more accurate picture of the direction in which the world is moving with regard to nuclear weapons.
Looking at the overall trend, there has been a consistent reduction in the “total number" of nuclear warheads since the end of the Cold War. At its peak in 1987, there were nearly 70,000 nuclear warheads in the world. Through agreements between the U.S. and Russia to reduce their arsenals, this number has been significantly reduced. From 2013, when the poster was first introduced, to the present, the "total number" has fallen from 17,300 to 12,120, a reduction of 5,180 warheads (approximately 30%).
Yet looking instead at the trend for “deployable nuclear warheads," the number fell by only 617 warheads, from 10,200 in 2013 to 9,538 in 2024. Starting from 2018, moreover, this number has gradually increased.
One factor contributing to the increasing trend was the arrival of the February 2018 implementation deadline of the New Strategic Arms Reduction Treaty (New START) between the U.S. and Russia. While the total number of warheads has decreased, actual progress in nuclear disarmament has not advanced significantly.
The arms control and disarmament treaty between the U.S. and Russia, which came into effect in February 2011, sets a limit on the number of deployed strategic nuclear warheads to 1,550 for each country. Both nations met this target by the implementation deadline in February 2018. The treaty is set to expire in February 2026, and there are no indications that a follow-up treaty will be concluded by then.
Despite the decrease seen in the “total number" of nuclear warheads, the trend in the “number of deployable nuclear warheads" indicates an ongoing “nuclear arms buildup," as previously explained. This issue, however, involves more than just the numbers. Nuclear-armed countries, led by the U.S. and Russia, are investing substantial budgets into “nuclear modernization programs" to update their aging nuclear systems with the latest technology. We also see, apart from the modernization of existing weapons, an acceleration in the development of new types of nuclear weapons using forefront technologies. Thus, the nuclear arms buildup is advancing not only in terms of quantity, but also quality.
When we speak of “modernizing,” we mean the process of maintaining and managing aging Cold War-era nuclear weapons systems by replacing and updating outdated components. This effectively enhances their capabilities. Modernization extends beyond nuclear warheads to include missiles, bombers, submarines, and nuclear testing facilities, among other things.
The poster shows the changes in the number of deployable nuclear warheads in each country over the six-year period from 2018 to 2024. The countries with the highest rates of increase are North Korea (233%), China (108%), India (36%), and Pakistan (21%). While the rates of increase for Russia and the United States are relatively low compared to these countries, it is important to understand that Russia and the U.S. together hold an overwhelming 80% of the world’s deployable nuclear warheads.
While the United States is the only country among the nine to have reduced its numbers, it is steadily advancing its nuclear arsenal in terms of “quality,” as previously mentioned. None of the nine countries are willing to relinquish their nuclear weapons; all are preparing to retain them for decades to come.
The poster shows the changes in the number of deployable nuclear warheads in each country over the six-year period from 2018 to 2024. The countries with the highest rates of increase are North Korea (233%), China (108%), India (36%), and Pakistan (21%). While the rates of increase for Russia and the United States are relatively low compared to these countries, it is important to understand that Russia and the U.S. together hold an overwhelming 80% of the world’s deployable nuclear warheads.
While the United States is the only country among the nine to have reduced its numbers, it is steadily advancing its nuclear arsenal in terms of “quality,” as previously mentioned. None of the nine countries are willing to relinquish their nuclear weapons; all are preparing to retain them for decades to come.
All nuclear-armed countries assert that possessing nuclear weapons is necessary to ensure the safety and security of their own homelands and those of their allies. When potential adversaries pose an ongoing nuclear threat to a country, a nuclear arsenal at home capable of inflicting devastating damage on those adversaries at any time is thought to deter attacks. This concept is known as “nuclear deterrence." Nuclear-armed countries believe that strengthened nuclear deterrence is the best strategy for their security. A nuclear arsenal is also seen as a demonstration of national power that gives a country an advantage in diplomatic negotiations.
The nuclear-armed countries and the 30 countries or so protected under their “nuclear umbrellas" share the view that nuclear weapons are indispensable for their security. Japan, which depends on the “nuclear umbrella" provided by the U.S., is one such country.
The formal term is “extended nuclear deterrence." The idea is to deter attacks on a non-nuclear ally by showing that the nuclear-armed ally will respond with nuclear weapons. Countries under the U.S. “nuclear umbrella" include Japan, South Korea, Australia, and non-nuclear NATO members. Belarus is under Russia's “nuclear umbrella."
With the progress of science and technology, the capabilities of today’s nuclear weapons are vastly more advanced than those of 79 years ago. On average, the explosive power of modern nuclear weapons is several to tens of times greater than the atomic bombs used on Hiroshima and Nagasaki. By today's standards, the bombs dropped on Hiroshima and Nagasaki can be considered 'small' nuclear weapons.
The variety of nuclear weapons has also greatly expanded. The development and deployment of forefront nuclear weapons with advanced capabilities, such as high-speed, long-range flight, and precision targeting across land, sea, and air, have been progressing.
The atomic bomb (A-bomb) is a nuclear weapon that uses the energy released when the nuclei of uranium or plutonium atoms split in a process known as nuclear fission. Another type of nuclear weapon, the hydrogen bomb (H-bomb), harnesses the even more powerful energy released when hydrogen nuclei fuse together. The “Little Boy" A-bomb dropped on Hiroshima used highly enriched uranium, while the “Fat Man" A-bomb dropped on Nagasaki used plutonium. Modern nuclear warheads use both highly enriched uranium and plutonium.
The memory of the atomic bombings of Hiroshima and Nagasaki reminds us of what would happen if even a single nuclear weapon was to be used, and how it would cause long-term suffering for people.
In addition, over the last few years, several research institutions have released damage assessments for various scenarios involving the use of nuclear weapons. Princeton University in the United States, for example, created 'PLAN A,' a simulation video based on a realistic nuclear war plan. The simulation predicts that a nuclear conflict between Western countries, including the United States, and Russia could escalate into a full-scale nuclear war resulting in over 90 million casualties within just a few hours of the conflict's onset.
Other research findings indicate that nuclear war has the potential to change the global climate. According to a study led by Rutgers University, a full-scale nuclear war waged between the U.S. and Russia would release vast amounts of soot and dust into the atmosphere, causing temperature drops severe enough to devastate crop production. The resulting global scale starvation could potentially lead to the deaths of more than 5 billion people.
According to estimates from a damage assessment published by RECNA et al. on the use of nuclear weapons in the Northeast Asia region, the death toll in affected areas could reach several million within a few months of an attack. Additional deaths resulting from the effects of radiation and other factors could rise to several hundred thousand over the time frame of a year or longer.
Nuclear weapons are, in a sense, precision machinery. The first step in dealing with them is to dismantle and dispose of them to ensure they can never be used. Just as with their manufacture, the dismantling process requires extremely careful handling to prevent the leakage of design information or fissile materials.
The dismantling, however, is just the beginning. The next issue is the fissile materials themselves, which do not simply disappear. Steps must be taken to ensure that these materials will never be reused in nuclear weapons. This can involve converting them into fuel for nuclear power plants (in the case of highly enriched uranium) or disposing of them as nuclear waste deep underground (in the case of plutonium). These are extremely challenging tasks that require international oversight. And in spite of the efforts so far taken, the amount of nuclear material in the world continues to increase.
Calculating the cost of producing a single nuclear weapon is far from straightforward. The cost can vary significantly depending on whether a country already possesses many nuclear weapons or is starting development from scratch. Also important are the technological capabilities of the country, as well as the various types and capabilities of the nuclear weapons that can be built. Altogether, these factors make it difficult to come up with a general estimate on cost.
For reference, the U.S. atomic bomb development program, the Manhattan Project, involved an enormous expenditure of approximately $2 billion between 1942 and 1945 (equivalent to approximately 300 billion yen at an exchange rate of 150 yen per dollar). When adjusted to today’s currency value, this amount easily exceeds $30 billion (approximately 4.5 trillion yen at the same exchange rate).
To prevent the use of nuclear weapons, it will be essential to encourage and facilitate dialogue among countries, rebuild bilateral and multilateral arms control and disarmament frameworks, and halt the further acceleration of the nuclear arms race.
The rise in the number of “deployable nuclear warheads" since the February 2018 deadline for the implementation of the New START underscores the urgent need to establish a new arms control and disarmament framework to succeed the New START. And future U.S.-Russia negotiations will have to address not only reductions in nuclear warheads and delivery systems, but also “qualitative" disarmament issues such as the development of new nuclear weapons.
As we continue our work to avoid these immediate dangers, we must also remember that the only sure way to prevent the further use of nuclear weapons is to eliminate them completely. As long as nuclear weapons exist, the risk of their use, including the risk of nuclear accidents, remains. Once a nuclear weapon is used, there is a potential for escalation into a nuclear war that could lead to the extinction of humanity.
A world without nuclear weapons can only come to be through the efforts of all nations, not just nuclear-armed countries. The Nuclear Non-Proliferation Treaty (NPT), a cornerstone of international nuclear disarmament and non-proliferation, mandates in its Article VI that all countries pursue negotiations in good faith on effective measures relating to nuclear disarmament. It will be especially important for countries protected under the “nuclear umbrellas" of the nuclear-armed states, such as Japan, to shift their policies towards “security without reliance on nuclear weapons." One such effort is the move towards the establishment of the Northeast Asia Nuclear Weapon-Free Zone.
For more detailed recommendations, please visit the RECNA website.
