For over 75 years, the US nuclear umbrella has been a cornerstone of global security, deterring adversaries and reassuring allies. Today this foundation is under unprecedented stress.

The world has entered a new era where old certainties are fading and nuclear risks are rising. As the United States faces a critical juncture regarding its global role and the purpose of its nuclear arsenal its allies confront new vulnerabilities in the nuclear crosshairs of emboldened rivals.

A new strategic reality

Longstanding assumptions about extended nuclear deterrence are tested as never before. The strategic environment once shaping America’s approach has fundamentally changed, necessitating a move beyond the vintage version of the US nuclear umbrella. Both Moscow and Beijing flex their strategic muscles, and the United States now faces two nuclear-armed peer competitors with rapidly expanding arsenals. Meanwhile, technological advances transform warfare and erode traditional advantages underpinning US security guarantees.

The familiar playbook of extended deterrence, crafted after World War II and refined during the Cold War, is increasingly ill-suited to multipolar nuclear competition. Allies and adversaries both question the credibility and effectiveness of US commitments. Meeting this moment requires a fundamental reassessment and modernization of US extended deterrence to ensure it remains robust, adaptive, and capable of addressing complex challenges.

Allies in the line of fire

As Russia and China integrate nuclear threats into their strategies, US allies in Europe and the Indo-Pacific find themselves in the nuclear crosshairs. If Washington falters, alliance cohesion could unravel, surging the risk of nuclear proliferation.

Anxiety is palpable: For European allies, Russia’s saber-rattling—recently seen in the context of Ukraine—revives fears about the credibility of American guarantees. In the Indo-Pacific China’s rapid military modernization and assertive posture alarm Seoul, Tokyo, and Canberra. These allies know that in crisis they may be the first targets.

The psychological dimension of deterrence is often overlooked. Allies must believe in the US commitment—when doubts creep in, the temptation to seek independent nuclear capabilities grows, threatening the nonproliferation regime and undermining decades of careful alliance management. Extended deterrence is not just about hardware and strategy—it is about trust.

Four strategic paths

The United States faces a series of strategic choices, each with its own risks, benefits, and far-reaching implications:

1. Reduce US commitments
   Scaling back nuclear guarantees might ease the burden on American resources, but risks weakening alliances, emboldening adversaries, and prompting allies to consider their own nuclear arsenals. US credibility would be called into question, and the global security architecture could unravel.
2. Expand guarantees
   Offering extended deterrence to more countries could strengthen collective security but stretch US capabilities and risk entanglement in regional conflicts. The more promises America makes, the harder they become to keep—especially in a crisis. Adversaries may respond with arms buildups or even provocations.
3. Maintain the status quo
   Sticking to current commitments risks ignoring a rapidly changing threat landscape. The “two-nuclear-peer problem”— possible simultaneous challenges from Russia and China—could strain US resources and force greater reliance on nuclear weapons.
4. Establish a new division of labor
   Encouraging allies to take on greater responsibilities offers a path to sustainability and more equitable burden-sharing but requires difficult conversations and institutional change. Allies must be willing and able to step up, and the United States to relinquish some control.

None of these options fully addresses the central challenge: how to deter two nuclear-armed adversaries at once, without risking escalation or overextension. The margin for error is shrinking, with catastrophic consequences for miscalculation.

A blueprint for the future

As I’ve written, the following steps are essential for adapting extended deterrence to today’s realities:

1. Adopt a comprehensive view of the threat—Allies must develop a shared understanding of the interconnected challenges posed by Russia and China, who increasingly blur the lines between conventional and nuclear conflict. This requires coordinated intelligence sharing, joint threat assessments, and regular strategic dialogues plus willingness to assume greater responsibilities. Since the actions of Russia and China are not confined to a specific region closer cooperation among allies—across Europe and the Indo-Pacific—is essential.
2. Leverage alliances as force multipliers—With finite resources, the United States cannot manage simultaneous conflicts with two nuclear peers alone, making strong alliances essential to extended deterrence. US alliances provide critical capabilities, amplify American strength, and ensure collective defense is effective in practice. Per Brad Roberts: “In a world where opportunistic aggression by a second nuclear-armed adversary is a real possibility, allies must be able to compensate when US focus and forces are drawn elsewhere.” The free riding era is over.
3. Rebalance collective capabilities—Identify gaps and let allies fill them—not just through increased spending, but by providing real operational needs. A clear, well-articulated division of labor is overdue. This means determining which specific forces, capabilities, and deployment timelines are required, and forthright discussions with allies about how they can contribute more effectively within their own contexts—through additional nuclear systems in Europe, as the UK or France might provide, or bolstering regional deterrence with advanced conventional forces in the Indo-Pacific. These discussions should also include enhancing our ability to counter and deter limited nuclear use by adversaries in regional conflicts, and how allies can contribute to addressing this challenge.
4. Prioritize procurement and capability development—Procurement decisions must be made now, as long lead times—often 5-10 years—require early action and a prompt, well-designed division of labor. Immediate identification of short-, medium-, and long-term priorities is essential for conventional, cyber, space, and missile defense domains. Allied contributions can free US resources for critical contingencies, ensuring investments where they matter most. Joint research and development, co-production, and shared logistics further amplify collective capabilities.
5. Enhance interoperability and joint planning—Interoperability is non-negotiable. Joint training, co-production, and a robust defense industrial base ensure seamless allied operations. As the 2024 National Defense Strategy Commission emphasized, US force structure planning must account for allied contributions, with clear roles and missions defined in advance. US peacetime planning with allies would serve as a powerful tool, and they should also focus on how to signal during intra-war deterrence, dissuading adversaries from escalating once a conflict begins.
6. Strengthen communication and signaling—A robust communication strategy is necessary to ensure that statements with allies are clear and consistent, avoiding contradictions that could undermine regional deterrence efforts. The United States and its allies could focus on making strategic communications more global, considering the interdependencies among all theaters. Lessons learned from the War in Ukraine, port visits to South Korea, and trilateral military exercises should inform how intra-war signaling might differ in various theaters.

Navigating the nuclear crossroads

If America does not modernize and rebalance its extended deterrence strategy, the consequences will reverberate far beyond policy circles. Deterrence could fail, alliances could fracture, and the United States and its partners could find themselves dangerously unprepared when the next crisis erupts.

Recent events show how quickly the security environment can deteriorate. Russia’s invasion of Ukraine, China’s assertiveness in the South China Sea, and North Korea’s ongoing provocations remind that regional deterrence is a dynamic challenge. The United States must be ready to adapt quickly and decisively.

Lessons from decades of US extended nuclear deterrence practices reveal a complex landscape of successes and shortcomings. Extending deterrence and assuring allies remain challenging policy endeavors. Since the end of the Cold War, the United States has continuously adjusted and adapted its alliance commitments across different regions, particularly in Europe and East Asia. The United States never achieved a “perfect” implementation of this strategy and extended nuclear deterrence enterprise endures constant shocks as alliances ebb and flow, and external factors frequently necessitate adjustments. One key success of extended nuclear deterrence has been its ability to adapt to shifting geopolitical realities. In a multipolar nuclear world, adaptation is not optional—it is imperative.

To succeed, the United States and its allies must:

• Institutionalize a new division of labor: Allies must take on greater responsibilities—by increasing spending and enhancing capabilities, integration, and leadership. The US should encourage regional powers to lead where they have the greatest stake and expertise. Allies are eager to do more but initial discussions have yet to produce meaningful rebalancing. Properly institutionalizing this new division of labor is essential for sustaining effective extended nuclear deterrence.
• Invest in interoperability and capability development: Deterrence depends on seamless cooperation. Joint procurement, shared logistics, and integrated command structures ensure allied forces can operate as one in any crisis.
• Bolster strategic communications: Deterrence is as much about perception as reality. The United States and allies must communicate clearly and consistently to both adversaries and their own publics—mixed signals invite risk.
• Prepare for the unexpected: The next crisis may not look like the last. The United States must invest in resilience, flexibility, and innovation so that its extended deterrence strategy can adapt as new challenges arise.

The road ahead

US extended nuclear deterrence has not kept pace with today’s rapidly evolving security environment. For three administrations, a “steady as she goes” approach has prevailed, but in a multipolar, two-peer world, this is no longer tenable. Allies are in the nuclear crosshairs, and adversaries test deterrence’s limits.

Choices made now will shape global security. Building on the legacy of extended deterrence, embracing a sustained and clearly defined division of labor, investing in interoperability, and sharpening strategic communications can meet the challenges ahead and keep the peace despite the nuclear crosshairs.

PacNet commentaries and responses represent the views of the respective authors. Alternative viewpoints are always welcomed and encouraged.

Paige Gasser ([email protected]) is Senior Fellow at the Center for Global Security Research at the Lawrence Livermore National Laboratory. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or Lawrence Livermore National Security, LLC, and shall not be used for advertising or product endorsement purposes. Release number: LLNL-MI-2013815.

Photo: Two U.S. Air Force B-1B Lancers fly with Koku Jieitai F-2 fighter , July 7, 2017 || Credit: Japan Air Self-Defense Force