The public is perceiving that nuclear deterrence is back on the international agenda. Even though the idea of a nuclear-weapons-free world is a laudable goal, the harsh realities in Europe and Asia unfortunately do not point to it being achieved soon. In Europe, Russia has put an end to the existing regional security order with its aggressive political stance and rhetoric towards its neighbours. NATO is of the view is that the concepts of deterrence and collective defence must again be underpinned by credible military capabilities and coherent strategies. Asia, for its part, considers that the problem of deterrence was never off the agenda anyway due to the large number of nuclear powers in the region and that it has gained a particular urgency through North Korea's nuclear ambitions – not to mention Trump's and Kim's aggressive rhetoric. Iran is another important factor in terms of nuclear weapons, missile programmes and deterrence, and how it will develop after the US withdrawal from the nuclear agreement is unclear.

"Extended deterrence” is a concept according to which the USA – as a nuclear power – has given security guarantees for its non-nuclear allies in both Europe and parts of Asia. This, by the way, does not only mean that the concept of extended deterrence ensures a broad portfolio of nuclear weapons being kept to protect around 30 allies of the US; another aim is that of depriving them of a motive to develop nuclear weapons of their own. Both regions are therefore confronted with the fundamental credibility problem surrounding extended deterrence: How credible is a promise of security from the protecting power if it in turn has to reckon with retaliatory nuclear strikes by an aggressor as soon as it steps into the breach for a partner? The familiar Cold War era question of whether anyone would be prepared to sacrifice Chicago for Hamburg can be applied to the present-day situation in Europe and Asia.

Both regions are also confronted with the changes in America’s alliance policy under President Trump. By imposing conditions on the validity of assurances of security – such as political compliance or financial contributions –, the new president is further undermining extended deterrence, since assurances of assistance – whether nuclear or conventional – must always be unconditional in order to cause the intended deterrence and reinsurance effects in allies and adversaries.

Finally, both regions have problems with public acceptance of the idea of nuclear deterrence. This is understandable in view of the insoluble dilemma associated with the concept. Nuclear deterrence can help to prevent conflicts because it contains the threat of unacceptable damage, but it must not fail, since the consequences of any use of nuclear weapons would be catastrophic. Public criticism is sharpened by the promotion of a nuclear-weapons-free world that its supporters believe could be achieved in the foreseeable future if only the political will were there to do so. No-one denies that a world without nuclear weapons would be a better one and that that the long-term goal should be to achieve complete nuclear disarmament. With respect to the foreseeable future, however, a nuclear-weapons-free world will remain an illusion. Nuclear weapons will instead remain a factor in international politics. In this respect, they also reflect the tense multipolar relationship between the states and account for why the problems of nuclear deterrence cannot be ignored.

During the discussions held on this basis, the conference in Seoul revealed that there is common ground, but also fundamental differences in the perceived role and understanding of nuclear deterrence. Six summarising findings can be identified.

1. Nuclear deterrence is a highly political issue

Extended deterrence in particular is a political and partly well-nigh theological concept: It is based only in part on the existing nuclear weapons and to a far greater extent on beliefs and trust in the guarantor power. Communicating and sending out signals to adversaries and, even more so, to allies thus become issues of huge importance. This is why incautious statements and ambiguous signals from the US administration – not to mention spontaneous Twitter messages – have such high relevance and possibly devastating consequences for both Europe and Asia. Europe and Asia are suffering from the unclear communication and disjointedness of the Trump administration. It is also clear in both regions, however, that this problem will probably be only partly solved under a successor of Donald Trump. The US has been creeping out of world politics for quite some time now, and a future US president will probably also want to reduce America’s role as a power that guarantees a value-based world order.

2. Nuclear deterrence must be tailor-made

There is no "one size fits all" approach to deterrence – each one must be specially devised for the respective region and situation. In Europe, this is comparatively easy because Russia's potentials and the principles of its strategic thinking are known. There is a tradition of cooperation and communication even in times of tension, with tried and tested crisis reduction procedures – right up to the various versions of the "red telephones". Moreover, the SALT, START and INF negotiations have provided experience in limiting certain types of nuclear weapons.

Tailored deterrence, as it is called in expert circles, is much more difficult with regard to North Korea. There is no more than rudimentary knowledge available on the state of development of the country’s nuclear weapons. There is difficulty in assessing the success of nuclear tests from the outside and there is only partial knowledge available on the extent to which this development, from the miniaturisation of nuclear test set-ups to usable long-range weapons, has progressed. There are not even any crisis communication tools. This makes nuclear deterrence difficult and always exposes it to the risk of misunderstandings and misinterpretations.

3. A say in nuclear matters is a must for South Korea

The delegates from Korea above all complained that the question of credibility was being raised even more clearly in their country than in Europe, where extended deterrence goes beyond the pure security promise and is based on three pillars. Firstly, US nuclear weapons are stationed on European soil and are partly subject to the so-called "dual-key system", according to which Europe would provide the carrier aircraft in the event of their use. Secondly, concrete procedures for allowing NATO members a say in US nuclear planning have been developed within NATO since the 1960s. Thirdly, NATO regularly conducts exercises in which nuclear procedures are practiced and the non-nuclear members are familiarised with them.

There is nothing like this in the Asian countries that are under the US nuclear umbrella, and so neither in South Korea. Due to the absence of practical cooperation in nuclear matters, uncertainty about the reliability of America’s promises is greater there than in Europe – no matter who governs in Washington. This is why countries such as South Korea and Japan have long been calling for a more open US information policy towards its Asian allies and more influence on US nuclear planning and activities. The US has done very little to date to comply with this call.

South Korea is furthermore of the view that more influence on US deterrence policy is also necessary if the current thaw between the North and South proves to be permanent and a reduction in the North Korean nuclear threat becomes possible. Irrespective of current decisions, it would take years to implement and verify nuclear disarmament steps in North Korea. In view of the lack of clarity surrounding Pyongyang's nuclear capabilities, there is also the question of how verification measures could be conducted in the world's most isolated state. It is also unclear whether the Kim regime itself would survive a cautious opening of the country and an easing of the pressure on its people. Consequently, South Korea is far from euphoric about the signals coming from the North and continues to see itself as being dependent on nuclear assistance from the US.

4. The prospects for denuclearisation vary

A look at the future of nuclear deterrence shows there is a fundamental difference between Germany and Europe on the one hand and South Korea on the other. In Seoul, there are cautious hopes that the rapprochement between the North and South will be successful. It may be several years before verification can be obtained of whether North Korea’s willingness to reduce its arsenal is serious because it will take some time for verification mechanisms to take effect in this completely withdrawn country. If this were achieved, however, the reunification of Korea – under whatever circumstances – would be conceivable. If such a step were taken, it would resolve not only the intra-Korean dispute, but also the nuclear threat issue. In a best-case scenario, it would also remove the need for US nuclear deterrence or extended deterrence – at least for a united Korea, if not for other countries such as Japan against China.

The situation is fundamentally different in Europe. Russia has destroyed its neighbours’ trust for a long time to come with its policy since the annexation of Crimea. Even if a possible successor were to return to the partnership policy pursued until 2014 after the end of Vladimir Putin's presidency in 2024, Russia's enormous nuclear potential would remain. Considering the distrust felt towards Russia, in particular by the Eastern European NATO members, the US nuclear umbrella would need to be retained for very many years to come.

5. The nuclearisation of South Korea is conceivable

Depending on events in Korea, an enlargement of nuclear arsenals in the region cannot be ruled out. In case the current rapprochement between the North and South should once again fail, the possibility of South Korea at least temporarily leaving the Nuclear Non-Proliferation Treaty (NPT) in order to procure its own nuclear weapons has not been ruled out. The country says that the technical prerequisites are in place and the political will is there, while the action that would be taken depends on how the threat from North Korea develops or whether the US promise of protection further weakens. Germany has pointed out the dangers of such a step because it would not only send a deterrent signal to North Korea, but also be perceived as a threat by neighbours such as Japan or China. Japan, too, is capable of developing its own nuclear weapons in quite a short time. The consequences for stability in the region would be hard to predict.

6. Chances of nuclear disarmament beyond the two Koreas are rather poor

Apart from the conceivable reduction in the North Korean nuclear arsenal, the chances of nuclear disarmament in Europe and Asia are rather poor. Russia has little interest in reducing its nuclear arsenal in Europe for a number of reasons, regarding it – and this is part of Russia's strategic thinking – as an integral part of its military potential and as compensation for its lack of conventional strength. Moscow also views nuclear weapons as one of the last symbols of its one-time role as a superpower.

In Asia, the idea of nuclear arms control is hard to implement in general because there seems to be no tradition of nuclear disarmament there. This is probably also due to the fact that a situation comparable to the Cuban Missile Crisis of 1962, in which the superpowers looked into the nuclear abyss of mutual destruction, has never arisen in Asia. Furthermore, the nuclear players in the region regard nuclear weapons as a "treasure" they went to the greatest trouble to acquire in order to serve their security interests. It is almost impossible to convey to them the necessity to give up even parts of this symbol of national grandeur.

Conclusions

The European-Asian nuclear dialogue has made it clear that nuclear deterrence is by no means a thing of the past, as has long been said in Germany in particular. The nuclear genie cannot be forced back into the bottle by the mere evocation of a nuclear-weapons-free world. Nuclear weapons fortunately no longer have the central significance for security that they had during the Cold War and have certainly lost value as a currency of power, but they will remain a factor in international politics. Consequently, credible deterrence concepts must be developed for both regions – with the prospect of détente at present putting South Korea in a special situation. NATO is already adapting its nuclear potential to the new realities. The key question of whom to deter and by what means can hence no longer be discussed behind closed doors in the NATO member states either.

Dr Karl-Heinz Kamp is the President of the Federal Academy for Security Policy in Berlin. This article reflects his personal opinions.