Extended Deterrence in a Multipolar World: Summary Report of the Symposium

Key Chapter Title List

Current Status and Key Drivers of Extended Deterrence

Topic 1: Escalation and Deterrence in 2025: Insights from Preliminary Wargaming

Topic 2: Russia, China, and U.S. Extended Deterrence

Topic 3: Regional Challengers and U.S. Extended Deterrence

Topic 4: Alliance Progress in Building Nuclear Capabilities

Topic 5: Evolution of U.S. Policy and Priorities

Topic 6: Managing Nuclear Crises

Topic 7: Nuclear Force Planning

Topic 8: Ensuring an Appropriate Mix of Deterrence and Defense Capabilities

Topic 9: The Future of Second Decision Centers

Document Introduction

This report is a summary of the Extended Deterrence in a Multipolar World workshop hosted by the Lawrence Livermore National Laboratory's Center for Global Security Research on March 25-26, 2025. The workshop brought together experts from policy, military, and technical fields to explore the applicability, challenges, and future adjustments of U.S. extended deterrence (including nuclear deterrence and broader aspects) against the backdrop of profound changes in the global security environment. Core issues included: whether U.S. extended deterrence remains fit for purpose in conflicts simultaneously involving multiple nuclear-armed adversaries; the impact of changes in the global security environment on the political and military requirements of extended deterrence; and how and what more allies can and should do to strengthen regional deterrence architectures.

Through nine thematic panel discussions, the report systematically analyzes multiple dimensions of extended deterrence. Participants first analyzed the macro context of how extended deterrence has evolved from a peripheral issue for nuclear deterrence experts to a central focus, identifying the tri-polar competition with China and Russia, emerging nuclear threats from North Korea and Iran, and uncertainty in U.S. policy as key drivers. The wargaming session revealed tensions between allies' prioritization of threats in their immediate neighborhoods and ambiguous U.S. decision-making priorities when simultaneously managing multi-regional crises, highlighting practical challenges such as signaling and perception mismatches, and allies' fears of being downgraded.

Regarding major competitors, the report provides an in-depth comparison of how Russia and China assess and counter U.S. extended deterrence strategies. Both view it as an obstacle to maintaining U.S. dominance, but Russia focuses more on Europe, emphasizing political subversion and information warfare, while China focuses on the Indo-Pacific, employing more economic coercion and gray-zone operations. The report also analyzes the different approaches of the two regional challengers, North Korea and Iran: North Korea focuses on undermining South Korea's confidence in U.S. extended nuclear deterrence and has adopted a highly preemptive nuclear doctrine; Iran broadly uses proxies, wedge strategies, and sub-threshold gray-zone operations in the Middle East to diminish U.S. influence.

The report assesses the progress and shortcomings of alliances in enhancing nuclear IQ and improving nuclear consultation mechanisms, noting that while some achievements have been made through mechanisms like the Nuclear Consultative Group, serious gaps in nuclear expertise persist both among allies and within the U.S. itself. Furthermore, the report examines whether U.S. nuclear force planning is adequate for current challenges, concluding that existing theater nuclear arsenals are insufficient for a scenario with two nuclear peer adversaries, necessitating the development of new theater capabilities (e.g., SLCM-N) and better integration of conventional and nuclear capabilities.

At the policy level, the report discusses the potential impact of the Strategic Posture Commission Report, how allies can influence U.S. policy, and the complexities of managing nuclear crises. Finally, the report examines the dilemmas of ensuring an appropriate mix of deterrence and defense capabilities in Europe and the Indo-Pacific, and engages in a deep debate on the pros and cons of second decision centers (i.e., allies developing independent nuclear capabilities), weighing their potential deterrent utility against the risks of triggering a nuclear proliferation cascade.

Overall, the workshop summary concludes that extended deterrence under multipolar pressure is not a fixed posture but an increasingly dynamic process defined by perceptions, prioritization, and the narrow space for simultaneously maintaining credibility. The United States and its allies urgently need systematic adjustments in capabilities, credibility, and alliance coordination to address an increasingly complex and dangerous security environment.