Nuclear security in a world of multiple challengers: Insights from MSC 2025

At this year’s Munich Security Conference (MSC), nuclear security took centre stage in a high-level, off-the-record discussion titled "Deterrence Decoded: Mapping Nuclear Modernisation in a World of Multiple Challengers." Moderated by Marina Henke, Director of the Centre for International Security and Professor of International Relations at the Hertie School, the event—held in collaboration with the Henry A. Kissinger Centre for Global Affairs at Johns Hopkins SAIS—brought together leading experts to examine how nuclear-armed states are reshaping global security.

In a recent interview, Henke shared key takeaways from the discussion, including how US nuclear modernisation (the process of upgrading nuclear weapons and strategies to counter new threats) is changing the global deterrence landscape. She also highlighted what this means for Germany and Europe, and the difficult choices ahead in balancing modernisation with non-proliferation efforts (the goal of preventing more countries from developing nuclear weapons).

How will the US nuclear modernisation programme change the global deterrence landscape?

The US nuclear modernisation programme is driven by two key logics: the rise of multiple nuclear challengers and new technologies. During the Cold War, nuclear deterrence focussed on the Soviet Union, but today’s landscape is more complex. China, once with 200 warheads, is reportedly aiming for 1,000 in the coming years, while North Korea has a functional nuclear arsenal, and Iran remains a potential nuclear actor.

Unlike the past, when nuclear assets were positioned for a Soviet threat, the US must now prepare for challenges in the Pacific and beyond, requiring a reassessment of force size, positioning, doctrine and strategy. At the same time, evolving technologies like hypersonic missiles, cyber threats, and potential space-based nuclear weapons pose new challenges. Right now, everything the US does comes down to adapting to this increasingly complex and unpredictable nuclear landscape—one defined by multiple nuclear adversaries and new technological challenges.

How should Germany and Europe modernise and evolve for the new nuclear age?

Germany has been part of a US nuclear sharing agreement since the 1960s, but with signs of reduced US involvement in European security, it’s worth considering if Europeans can still really rely on the US nuclear umbrella. There are two possible scenarios for a US withdrawal from Europe: one focusses on a substantial cutback in US conventional forces stationed in Europe. The more extreme scenario would involve the US also withdrawing its nuclear umbrella, which of course would be even more dangerous for Europe. Why? Because Europe faces a nuclear antagonist: Russia, which heavily relies on its nuclear forces and frequently employs nuclear rhetoric and threats. Without US nuclear protection, the risk substantively increases that Russia uses its big nuclear arsenal to blackmail Europe. 

If the US does withdraw its nuclear umbrella, Germany must consider alternative options. One possibility is nuclear sharing with France and/or the UK, but their arsenals are much smaller than the US's—France has around 200 warheads, while the US has 4,000. To be viable, both the UK and France need to increase their arsenals. One also needs to think about what such nuclear sharing would look like. The Franco-German-Italian AFCAS project, which is developing a new fighter jet, could, for example, include the certification of those planes to carry French nuclear weapons, in a set-up similar to that of the US today. 

How should the West balance between nuclear modernisation and nuclear non-proliferation?

That’s a tough question. Until now, the US has based its arms control negotiations on the idea of maintaining “strategic stability”, meaning that both major nuclear powers, the US and Russia, should maintain roughly equal-sized arsenals. But now, you have to consider the growing nuclear threats from China, North Korea, and potentially Iran. If these countries collaborate—something we’re already seeing signs of—the US may have to account not just for Russia’s arsenal, but also China’s expanding one, North Korea's small arsenal, and Iran’s potential growth. If the US increases its nuclear weapons to maintain balance, it could spark a new arms race. 

From Europe’s perspective, if the US were to withdraw its nuclear umbrella, countries like Poland, the Baltic States, or even Ukraine might feel compelled to develop their own nuclear weapons for self-defence. This could trigger a cascade effect, with countries like South Korea and Saudi Arabia following suit. Since the US has invested heavily in preventing nuclear proliferation since the 1960s, its decisions are critical. If it withdraws, we might see a dramatic rise in nuclear states globally, underscoring how much responsibility the US bears in this issue.

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