Trump and Asia: Tokyo and Seoul Proliferation Prospects

Amid worrying remarks from President-elect Donald Trump and North Korean provocations, there are growing fears that Japan and South Korea might seek to acquire a nuclear capability. However, this anxiety is misplaced, for it does not take into account the political and technical options available to Tokyo and Seoul.

Following the two nuclear tests from North Korea this year, discussion about the nuclear prospects of Seoul and Tokyo has re-emerged. This has received further impetus by the rhetoric from US President-elect Donald Trump, who during his electoral campaign warned Washington’s Asian allies that they could not rely on ‘free-riding’ on America’s military capabilities for their own defence.

Extended deterrence policies have, for decades, been a rare subject of bipartisan consensus in Washington, a source of comfort for US allies in East Asia who were reassured that they were protected by America’s nuclear umbrella.

However, these allies are now aware that this can no longer be taken for granted. That realisation, coupled with the increased threat and the prospect of a North Korean nuclear retaliation against the US territory and homeland, has prompted both Seoul and Tokyo to question the ability and desire of Washington to manage a crisis abroad and carry through on its extended deterrence commitments.

Even if the US nuclear umbrella were to remain in place, they wonder whether America would be prepared to sacrifice San Francisco in order to retaliate for an attack on, say, Seoul? However, even with calls in South Korea and Japan for serious consideration of a move towards indigenous nuclear weapons, it still seems highly unlikely that either nation would incur the immense political costs that would come from withdrawing from the Non-Proliferation Treaty and from launching a ‘race for a bomb’.

Obtaining a nuclear capability is not a binary choice, but a matrix of both technical and political capacities. Although Japan and South Korea occupy different places along the capability spectrum, the leap across technical and political proliferation facets to acquire nuclear weapons remains, at present, too big for both Seoul and Tokyo. Irrespective of the regional nuclear threats Japan faces, Tokyo has unwaveringly maintained an outstanding record of non-proliferation. However, Japan is also positioned in technological terms very close to a nuclear weapons capability. It has maintained a full nuclear fuel cycle with both enrichment and reprocessing capabilities, as well as vast quantities of stockpiled, weapons-useable plutonium and uranium. ‘Nuclear hedging’ is the model of proliferation whereby a state intentionally moves its nuclear programme towards the weapons line without creating an outright nuclear weapons programme. Although this level of infrastructure has been maintained for peaceful purposes, Japan’s technical nuclear independence and highly advanced capabilities make it easier for Tokyo to pursue varied proliferation options, should the political impetus to pursue a model of proliferation be present. While the outcome and benefit of a rhetorical or signalling shift will be contingent on many external factors, including threat context and legal and normative restrictions, Japan’s nuclear infrastructure does grant Tokyo strategic flexibility across the proliferation spectrum.

However, the official political impetus to drive forward this technological capacity into a weapons programme is not present, and such flexibility does not equate to an imminent proliferation threat. The security context of Japan would need to alter significantly more than it has in recent months before consideration of the political leap to nuclear weapons can become a reality.

Domestic calls for nuclearisation have been louder in South Korea than in Japan, with a number of opinion polls indicating that over half of the voters may now favour developing a nuclear arsenal. Although current public preoccupation is with the political scandal embroiling President Park Geun-hye, this will not override the long-term movement of nuclear discussions away from the fringes to the centre of public debate.

Notwithstanding this, Seoul would face more practical hurdles than Japan to amending its non-proliferation policy, mainly as a result of two factors. First, South Korea sits at a lower level of technical capability – a fact deliberately engineered as part of civil nuclear cooperation agreements with the US.

In particular, South Korea is not permitted to reprocess plutonium indigenously – a key pathway to weapons-usable material. So although the political desire to explore the nuclear road, via hedging or otherwise, might be higher than in Japan, limited technical capacities reduce any imminent proliferation concern.

Second, South Korea is not able to amend or ignore this restriction without substantially damaging its alliance with the US. Seoul is so heavily dependent on its US alliance for conventional force and deterrence against Pyongyang that it is unlikely to want to jeopardise this support by officially suggesting or pursuing an independent nuclear arsenal.

Such a break would leave Seoul vulnerable for a period of time, lacking both the robust US backing that it has traditionally enjoyed as well as its own convincing capability. Irrespective of alliance calculations, disapproval from the broader international community would surely follow any apparent increase in South Korean or Japanese nuclear steps. How this disapproval would manifest itself and to what extent such policy shifts would invite tangible punishment is difficult to assess at the moment. However, the assumption is that the risk of backlash is likely to be decisive in favour of the status quo for both Japan and South Korea. In both cases, therefore, gaps between current status and weapons acquisition are too large to raise immediate proliferation concerns. From a purely technical viewpoint, Japan’s advanced nuclear infrastructure would provide greater flexibility for approaching proliferation, but dramatic political changes remain unlikely.


Banner image: South Korean and US soldiers monitor the Korean Demilitarised Zone from an observation post. Courtesy of Edward N Johnson/US Army Public Affairs.


Cristina Varriale

Associate Fellow

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