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

Key Chapter Title List

The Current State and Key Drivers of Extended Deterrence

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

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

Topic Three: "Regional Challengers" and U.S. Extended Deterrence

Topic Four: Alliance Progress in Building Nuclear Capabilities

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

Topic Six: Managing Nuclear Crises

Topic Seven: Nuclear Force Planning

Topic Eight: Ensuring the "Right Mix" of Deterrence and Defense Capabilities

Topic Nine: 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 is "fit for purpose" in conflicts involving multiple nuclear-armed adversaries simultaneously, the impact of changes in the global security environment on the political and military requirements of extended deterrence, and how allies can and should take more action to strengthen regional deterrence architectures.

Through nine thematic panel discussions, the report systematically dissects 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 great-power tri-polar competition between China and Russia, emerging nuclear threats from North Korea and Iran, and uncertainty in U.S. policy as key drivers. The wargaming session revealed the tension between allies' prioritization of threats in their immediate neighborhoods and the ambiguity of U.S. decision-making focus when dealing with multiple regional crises simultaneously, highlighting practical challenges such as signaling and perception misalignment, 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. 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 activities. 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 extensively uses proxies, wedge strategies, and sub-threshold gray-zone activities in the Middle East to erode U.S. influence.

The report assesses the progress and shortcomings of alliances in enhancing "nuclear IQ" and improving nuclear consultation mechanisms, noting that despite some achievements through mechanisms like the Nuclear Consultative Group, the gap in nuclear expertise among allies and within the U.S. itself remains severe. 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 dual-nuclear-adversary reality, 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 dilemma of ensuring the "right 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 risk of triggering a nuclear proliferation cascade.

Overall, the workshop concluded 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 maintaining credibility simultaneously. 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.