Hirofumi Tosaki is a senior research fellow at the Center for Promotion of Disarmament and Non-Proliferation, Japan Institute of International Affairs.
It is quite difficult to form a definitive answer to the question of whether the age of extended nuclear deterrence (END) is coming to an end, since END is inherently complex, and its complexity is increasing after the Cold War. But my answer is 'no' for the foreseeable future, unless the security situation, or US nuclear policies, or Northeast Asian policies, change dramatically. Take Japan as an example.
During the Cold War, what Japan ultimately expected END to do was deter threats posed by the Soviet Union to Japan's national survival as a liberal, democratic country. Currently, no such 'existential threat' exists. However, Japan has heightened its concerns about challenges to its national interest, such as issues of territory, maritime interest, regional and international order, and possible attempts by other counties possessing nuclear forces to change the status quo using their military powers.
In such a security environment, Japan, which maintains an 'exclusively defensive defense' policy and does not possess any capability to retaliate against other country's territory, expects US END to continue to play an important role of deterring a wide range of possible challenges to its national interest.
Japan has been concerned about the credibility of US END. There are possibilities of the US being deterred, of the stability-instability paradox increasing or even of Japan facing abandonment. This is because of the asymmetric scale of interests between the US and a certain adversary in the region, and that particular adversary's development of asymmetric capabilities, especially its acquisition or reinforcement of nuclear retaliatory capabilities against US forces and its homeland. However, this does not mean that END is becoming anachronistic or irrelevant.
As Bruno Tertrais suggests, it is inconceivable that an adversary, if rational, would fail to consider the possibility of US nuclear retaliation, however remote it is from the US, and even if it possesses a reliable second strike capability, when it comes to conducting even a limited military option against Japan.
Of course, we should not place exaggerated hopes on END, as US allies such as Japan have occasionally done. Even if the US maintains a robust defense commitment, including the provision of END, an adversary may conduct a low-intensity military option under deliberate consideration, or by miscalculation, misperception, overestimation of its capabilities, or even underestimation of US resolve. END is not a panacea, and we need to keep contemplating the roles and limits of END in a realistic manner.
END is indeed significant, but it is just one of various means for guaranteeing an ally's security and mitigating threats. Rather than just relying on END, it is imperative for Japan to reinforce its efforts, under close coordination and cooperation with the US, to construct stronger conventional capabilities — including addressing anti-access or area denial capabilities, developing missile defense and sharing roles, burdens and capabilities — for adequately deterring the low-intensity, limited challenges that Japan may face, as well as denying an adversary's escalation or achievement of objectives.
Such efforts will contribute to further enhancing Japan's own deterrent capability, the Japan-US alliance, and the credibility of US END.
Finally, END will become less and less imperative where military challenges or threat have been mitigated or have vanished. In achieving this goal, the importance of enduring efforts toward deepening strategic dialogues, developing transparency and confidence building measures, creating a communication mechanism in case tension heightens, and promoting arms control and non-proliferation are steadily but surely increasing in Northeast Asia.
The Nuclear Reactions column is supported by the Nuclear Security Project of the Nuclear Threat Initiative, as part of a wider partnership between the NSP and the Lowy Institute.
Photo by Flickr user Ciro@Tokyo
