The Nuclear Umbrella is Bent, Not Broken

Why Extended Nuclear Deterrence Still Matters

Jennifer Lind and Daryl Press make a compelling argument in a recent article about the future willingness of the United States to provide extended nuclear deterrence, sometimes referred to as the “nuclear umbrella” to over 30 allies. Since the early days of the Cold War, the U.S. made a commitment to defend Europe against Soviet aggression, and under extreme conditions, included the use of nuclear weapons. Similar assurances were made to Japan, South Korea and Australia. The protection provided by this nuclear umbrella has been a hallmark of international order for decades as allies trusted the U.S. would protect them and therefore had no reason to develop their own nuclear weapon capabilities. Lind and Press rightly point out the security environment has changed dramatically and the “order” created by the United States during the Cold War no longer exists. With the dissolution of the Soviet Union, Lind and Press argue Russia’s nuclear threat on a global scale is much diminished with Russia focused on its boundaries with eastern Europe and less concerned with “the global balance of power”. Similarly, Lind and Press view North Korea’s nuclear weapons development as a regional security issue with Kim Jong Un more interested in regime survival than peninsular conquest. They further argue conflicts today are largely regional in nature and question the commitment of the United States to engage in a nuclear conflict on behalf of an ally thousands of miles away. Thus, they claim the “nuclear umbrella” is broken.

The Nuclear Umbrella Still Exists

On the surface, it’s easy to believe this argument. The first Trump administration clearly stated an intent to put “America First” in 2017 and the second Trump administration signaled skepticism toward alliance commitments and their associated costs. Abroad, there is potential that this signaling from Washington also includes the commitment to extended nuclear deterrence. President Trump’s new National Security Strategy (NSS) published in 2025 does not mention extended nuclear deterrence or the nonproliferation of nuclear weapons. Similarly, the 2026 National Defense Strategy (NDS) does not “explicitly mention extended deterrence” and instead places the “primary responsibility” for their own defense on them with limited support from the U.S. And lastly, the current Trump administration has not and most likely will not issue a Nuclear Posture Review (NPR). The first NPR was released in 1994 every subsequent administration has issued one until President Trump took office again in 2024. The NPR is a blueprint which describes the role of nuclear weapons in U.S. security strategy. This document contains critical messaging on the capabilities, numbers, and modernization efforts of nuclear weapons and under what conditions the U.S. potentially would or would not use nuclear weapons. To be sure, the absence of explicit language on extended nuclear deterrence in the NSS and NDS and the lack of an NPR are departures from the U.S.’s historical stance providing nuclear top cover and nonproliferation of nuclear weapons.

Allies and partners of the U.S. have obviously taken notice and started conversations on how to proceed especially given continued Russian aggression, Chinese and North Korean nuclear weapons development, and what they might perceive as uncertainty of the U.S. as a nuclear deterrent backstop.

The United Kingdom and France recently pledged increased cooperation with nuclear weapons with the signing of the Northwood Declaration in 2025. French President Macron also rolled out a policy of “advanced deterrence” aimed at potentially providing nuclear forces to various European allies. Additionally, Japan, South Korea and Australia are all deeply concerned about nuclear weapons development in both China and North Korea. As a result from the proximate threat, some Japanese and South Korean officials have publicly discussed nuclear weapons, a topic previously considered taboo.

However, there is also plenty of evidence to support the fact that while the nuclear umbrella is bent and tattered, it’s not broken.

Although the current NSS and NDS do not explicitly mention extended nuclear deterrence, they do not explicitly eschew the notion either. In fact, the NDS states Europe should take “primary responsibility for its own conventional defense…” making a clear distinction between conventional and nuclear forces. Despite much talk of NATO needing to pull more of its own weight regarding security, the U.S. remains committed to the alliance. Since 1954, the U.S. pledged to protect NATO members and currently has around 100 air-delivered nuclear weapons deployed to various bases in Europe. In addressing the NATO Defense Ministerial, Under Secretary of War for Policy, Elbridge Colby, stated, “Thus, for the United States, our responsibility is to be clear, candid and consistent. We will continue to provide the U.S. extended nuclear deterrent.” Additionally, the U.S. continues to be active in the NATO Nuclear Planning Group, the senior policy body for NATO nuclear issues. Despite U.S. signaling a “scaling back” of conventional support to NATO, there is no plan to remove any of these nuclear weapons from Europe.

There are similar extended nuclear deterrence concerns from Japan and South Korea, especially the suggestion that both should take on more of the financial burden for their defense, the U.S. commitment to both is bit clearer. In February of last year, the U.S. Secretary of State met with the Foreign Minister of Japan and the Foreign Minister of the Republic of Korea to “reaffirm the unshakable trilateral partnership” between the three countries. This meeting underscored the historical commitment of the U.S. to the defense Japan and South Korea to include extended nuclear deterrence.

Why Extended Nuclear Deterrence Matters

What’s missing in many of the arguments concerning U.S. extended nuclear deterrence is how it has underwritten the concept of nuclear nonproliferation for decades. In 1968, the U.S. pledged cooperation in limiting the spread of nuclear technology as one of the first signatories of the Nuclear Non-Proliferation Treaty (NPT). Though limited and certainly not perfect, the Nuclear Nonproliferation Treaty (NPT) is widely considered one of the most successful arms control treaties ever written by limiting the spread of nuclear weapons while aiding risk reduction of nuclear weapons use. As mentioned earlier, dozens of countries have chosen not to pursue development of nuclear weapons (and pledged not do so as signatories of the NPT) because they determined the extended nuclear deterrent guarantee provided by the U.S. to be reliable and most importantly, credible. Additionally, any country who may feel abandoned by the nuclear umbrella provided by the U.S. and may choose to pursue development of their own nuclear weapon faces myriad challenges. First, many are bound by the NPT and even if they were not, often lack the resources to develop nuclear weapons and delivery systems. Second, all states, even those with the technical know-how to proceed with a nuclear weapons program, would introduce into the nuclear “club” another independent launch authority, more command-and-control systems with varying levels of capability, unknown decision-making processes during crises, and more opportunities for proliferation, miscalculation, and accidents. Following the bombing of Hiroshima and Nagasaki, the one thing the international community could agree upon was developing a strong prohibition against the use of nuclear weapons. Many resolved crises throughout history where nuclear weapons loomed in the background reinforced the idea that the use of nuclear weapons was unthinkable. The spread of nuclear weapons to more independent states does not simply mean we live in a world with more of them, it substantially increases the number of situations where they become increasingly integrated into routine statecraft and thus, their potential use more thinkable.

The Strategic Consequences

Despite concerns about the credibility of U.S. extended nuclear deterrence that have emerged in some allied capitals, the United States should not become resigned to the prospect of allies leaving the nuclear umbrella. Doing so would weaken the nonproliferation regime, increase incentives for independent nuclear programs, and ultimately leave the United States confronting a more dangerous strategic environment. The U.S. should continue to signal that the credibility of extended nuclear deterrence rests upon strong conventional capabilities and even stronger, unmistakable political resolve with our allies while keeping nuclear use as the final safeguard. Increased proliferation of nuclear weapons does not achieve that objective.

The United States is unique among states that possess nuclear weapons because it has used the world’s most capable nuclear weapons arsenal to prevent nuclear proliferation rather than encourage it. Thus, extended nuclear deterrence and nuclear nonproliferation are inseparable. The enduring contribution to international security by the United States has been and should continue to be the guarantee of nuclear extended deterrence to uphold nonproliferation and preserve the longstanding objective of nuclear non-use.

In no uncertain terms should the U.S. become “comfortable” with more states acquiring their own nuclear weapons resulting from of a lack of confidence that Washington will continue to be the nuclear guarantor. Despite periodic political signals that make some allies nervous, Washington has been remarkably consistent, across multiple administrations, in its policy toward extended nuclear deterrence. States that question U.S. commitment should consider whether other alternatives would enhance their security. The answer is almost certainly no.

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