Why the U.S. Nuclear Umbrella Underpins Non-Proliferation

The protection-for-abstinence bargain propping up the nuclear umbrella relies on allies and adversaries believing that the U.S. has the will to risk nuclear retaliation against the homeland to defend distant friends. Even today, a handful of NATO allies host small quantities of sharable U.S. nuclear weapons on their territories to improve the credibility of deterrence.

But nuclear sharing is a European exception. In the Indo-Pacific, Bush’s announcement ended an era in which U.S. nuclear weapons had been present in allied territories for decades, either as deployments on land or in transit on U.S. Navy vessels. Following earlier withdrawals in the 1970s from Okinawa (ahead of its full return to Japan), Taiwan and the Philippines, the U.S. removed its last nuclear weapons from South Korea in 1991. Managing these forward deployments strained public trust and involved levels of secrecy and backroom dealings that are still emerging in the archives.

It’s possible that contingencies still exist for redeploying tactical nuclear weapons to forward locations in the Indo-Pacific. But, in the main, South Korea and Japan put their faith in public proclamations that the U.S. has the means and will to project nuclear force from afar in their defense, illustrated by the periodic appearance in the region of U.S. nuclear-capable bombers. Behind the scenes, bilateral consultations on extended deterrence thrash out details and align expectations.

Successive Australian defense white papers dating back to 1994 make clear that Australia also expects U.S. nuclear protection, even if Canberra seems less concerned than Seoul or Tokyo about soliciting U.S. assurances in public. Australia banned the stationing of nuclear weapons on its territory under the Treaty of Raratonga in 1986. However, the periodic operation of U.S. bombers from Royal Australian Air Force Base Darwin and longstanding shared access to intelligence and communication facilities in Australia, including Pine Gap and North West Cape, attest to an implicit quid pro quo that the price of coverage by the U.S. nuclear umbrella includes integration in nuclear planning and therefore the likelihood of being targeted. The same is true for Japan and South Korea.

Despite the implicit costs, the U.S. nuclear umbrella has remained attractive to allies because the alternatives have seemed unpalatable, at least during the phase after the Cold War when the risk of nuclear war felt relatively low.

Japan and South Korea are among the countries sometimes called latent nuclear powers because they probably possess the means to develop nuclear capabilities relatively promptly. This would be harder for Australia but not impossible, at least in theory. In practice, the economic, legal and political barriers to independently going nuclear remain prohibitive, and the Australian public is set against it. As strategists like Hugh White have argued, the main driver for Australia or other U.S. allies in the Indo-Pacific to overcome these hurdles in pursuit of nuclear weapons would be a breakdown of trust in U.S. protection.

In other words, the U.S. nuclear umbrella remains a lynchpin of non-proliferation in our region. As Australia’s 2017 foreign policy white paper says, ‘Without extended deterrence, more countries in the Indo-Pacific would need to re-assess their security and defense capabilities.’ That is official code for seeking weapons of mass destruction.

Unfortunately, allies will be watching Chinese and Russian actions and pondering whether the U.S. nuclear umbrella remains credible.

China under President Xi Jinping is rapidly expanding its nuclear forces and doing so outside an effective arms control regime. Unlike the U.S., Beijing is modernizing its forces without any transparency, which violates its obligations as a nuclear weapons state under the Non-Proliferation Treaty. Russia is not alone in deploying new weapons platforms that have potential nuclear applications, such as hypersonic missiles. But intentions and trustworthiness matter as well as the capabilities themselves, which is why President Vladimir Putin’s flagrant nuclear threats over Ukraine and obstructionism in multilateral forums put Moscow in a different category to Washington. Chinese and Russian nuclear forces have cooperated to some extent since the announcement of the Xi–Putin ‘no limits’ partnerships. Both countries have close ties to nuclear North Korea, which continues to test and improve its own nuclear forces.

So, how should Australia and the international community respond to our worsening strategic environment?

For a start, we mustn’t give up on international rules and norms or shy away from criticizing China and Russia for fear of being labelled biased.

In this light, it was heartening to see Foreign Minister Penny Wong prioritize non-proliferation initiatives and messaging, including calling out Moscow and demanding more from Beijing, during UN high-level week this month. Equally, Australian officials have said they want to work with the International Atomic Energy Agency to set the highest possible non-proliferation standards through the acquisition of nuclear-powered (not nuclear-armed) submarines under the AUKUS partnership. Such engagement has been welcomed by IAEA Director General Rafael Grossi. Given Japanese Prime Minister Fumio Kishida’s personal commitment to non-proliferation, there are opportunities for Canberra and Tokyo to work more closely together, including through the Non-Proliferation and Disarmament Initiative, which they co-founded.

Importantly, we mustn’t dislocate multilateral initiatives from strategic realities. This is one reason why Australian and Japanese leadership makes sense—both bring perspectives as, to quote the foreign policy white paper, nations that ‘rely on nuclear deterrence for their security’.

We have an opportunity to apply this more joined-up style of thinking as the U.S. works with its allies to develop the concept of integrated deterrence, which is a key component of the U.S. national defense strategy. In line with the nuclear posture review, nuclear forces are being modernized. Overall, however, nuclear weapons should play a reduced role in maintaining credible extended deterrence. Instead, more emphasis shifts onto conventional and hybrid capabilities, leveraging the U.S. network of allies and partners. This would support non-proliferation if it can be achieved.

Consistent with integrated deterrence, Australia, Japan and South Korea are already investing in capabilities like conventional long-range strike and offensive cyber. For Australia, AUKUS is crucial for achieving this—not just for submarines but also in the other areas of advanced technology cooperation. South Korea has perhaps gone the furthest by introducing a new command structure to implement the ‘three-axis’ system, which is intended to deter a North Korean nuclear attack through a combination of missile defence and conventional strike. These investments by U.S. allies are intended to complement rather than supplant the U.S. nuclear umbrella, which, in theory, is made more credible by becoming more clearly a last resort.

We don’t yet know how integrated deterrence will work in practice, but it seems evidently better for the cause of non-proliferation than other options being mooted to address the credibility of extended deterrence, such as reintroducing U.S. nuclear weapons to the Korean peninsula or allies pursuing sovereign nuclear capabilities.

We would all prefer to see a world with fewer nuclear weapons. In our current strategic circumstances, that requires finding a way to incorporate the non-proliferation benefits of the U.S. nuclear umbrella into multilateral initiatives.

Alex Bristow is deputy director of ASPI’s defense, strategy and national security program.This article is published courtesy of the Australian Strategic Policy Institute (ASPI).