How states view the roles and relevance of nuclear weapons is changing. While these perspectives have been dynamic since the dawn of the atomic age, the changes occurring today and drivers of these changes are particularly worrisome—in particular given that they seem to be on the cusp of reversing a period heavily characterized by arms control agreements, reductions in global arsenals, and advances in international cooperation to reduce nuclear weapons risks.   

CSR’s core nuclear policy work to address this challenging time has focused largely on qualitative approaches to reducing the risks of nuclear miscalculations, uses of these weapons, arms racing behavior, and other dangerous trends. Going beyond numbers of weapons—which has been a major policy focus given numerical limitations in past nuclear treaties—a qualitative view of the nuclear weapons landscape is done through the lens of the nuclear capabilities nations seek, and associated policies and postures. This can help to show where multiple nations might find areas for potential cooperation that would be mutually beneficial. It can also help to show where nations currently possess the capabilities they claim to need, and thereby in what ways cooperative or unilateral measures of restraint are the most appropriate.  

In order to facilitate this work by CSR and by others, we are launching The Nuclear Weapon Systems Project to help visualize how the types of nuclear capabilities fielded in the world have evolved since the advent of these weapons. 

This project seeks to document and characterize every deployed nuclear weapons system that NPT-recognized nuclear states have developed in history. More than just a list of bombs, missiles, and artillery shells, the resulting dataset illustrates a complex story of risks, strategies, and lessons learned—and lost. We consider this data to be a living resource, and encourage outside contributions and feedback.

For more on background, definitions, process notes, and limitations of this data, see our launch post.

Data last updated November 29, 2023.

As the visualizations show, focusing on qualitative changes in nuclear weapons over time shows that the early Cold War was characterized by the United States and Soviet Union racing to develop as many different nuclear capabilities as they could—a vast array of weapons for an incredibly wide range of potential uses. Many of these weapons were deployed, including to frontline conflict areas where their use was quite possible, including through accidents or miscalculations. 

However, for many types of nuclear weapons, it became clear that the risks that they brought were more detrimental to their possessing nation’s security and that of its allies—and this was likely to be the case for opposing countries making similar calculations. Through many steps over time, world leaders halted the trend of continually fielding more types of nuclear weapons. In addition to the number of nuclear weapons declining over time, this trend helped to drive decades of relative stability. The history of this accomplishment is rich with lessons for today’s world.

As the data also reveal, the world is now risking moving back toward the dangerous, more-expansive nuclear-capabilities landscape that it effectively turned away from. This alone proves the value of understanding the qualitative nuclear weapons changes that may be forthcoming if not addressed. 

This approach can also help us to focus on solutions by revealing changes in the nuclear landscape that are likely to unnecessarily increase risks. More so than numbers alone reveal, a qualitative approach can show where entanglement is increasing or decreasing, where offense-defense balances are evolving, what types of weapons may be perceived as relative continuity or game-changing to other countries, and more.

For now, The Nuclear Weapon Systems Project focuses on the P5 countries that are defined as nuclear weapons states under the Nuclear Non-Proliferation Treaty. This project has also been shaped by varying levels of nuclear weapons information across these states, different interpretations of the perceived roles of these weapons, and other factors.  

As you explore this resource, please watch for CSR analysis stemming from this data, and see our launch post for further project background, definitions, process notes, and limitations of this data.

---