In no country does opposition to nuclear weapons run deeper than in Japan. The nuclear attacks on the Japanese cities of Hiroshima and Nagasaki at the end of World War II in August 1945 instilled in Japanese society a horror of these armaments that persists, strongly, nearly 75 years later. Three non-nuclear principles are embedded in the country’s public life. The Japanese have forcefully and repeatedly disavowed possessing and producing nuclear weapons and permitting them to enter their country. Despite this pronounced aversion, however, Japan is moving toward the serious consideration of acquiring these weapons of mass destruction. Or rather, and more accurately, Japan is being pushed in that direction by the policies of three countries whose policies bear heavily on its security: North Korea, China, and the United States.

Since World War II Japanese security policy has rested on two pillars: Article 9 of its Constitution, which asserts that “The Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes;” and an alliance with the United States that has provided Japan with American protection against attacks by third countries.

Until recently the combination proved remarkably successful. It made Japan secure without the need for powerful armed forces of its own. It reassured Japan’s neighbors that they had no need to fear a repetition of the brutal campaigns of conquest that Japan conducted at their expense during the 1930s and 1940s. In those circumstances Japan flourished economically, building the second-largest economy in the world and achieving an enviable standard of living. 

To be sure, Japan has not spent the last three-quarters of a century as an entirely disarmed, resolutely pacifist member of the international community, as Sheila A. Smith’s timely and useful book Japan Rearmed: The Politics of Military Power makes clear. Smith, a senior fellow at the Council on Foreign Relations, recounts the adjustments to military policy that the country has made, always slowly and deliberately and sometimes after spirited political battles, since the 1950s.

The Japanese have interpreted Article 9 as permitting them to have armed forces and over the decades have built an army, a navy, and an air force that together constitute, in Smith’s words, “one of Asia’s most formidable militaries.” They have deployed their military personnel abroad, although for peace-keeping operations rather than for war. They have expanded military cooperation with American forces in Northeast Asia. The Self Defense Forces, as the Japanese military is called, have earned the respect of the Japanese public. 

Still, Japan’s armed forces remain limited in size and in the operations that they can conduct, and have never, since 1945, engaged in combat. Nor has the country seriously debated equipping them with nuclear weapons. Now, however, North Korean and Chinese military initiatives, along with uncertain American attitudes toward the alliance with Japan, threaten to change all this.

Communist North Korea, only 600 miles from the Japanese archipelago, has steadily developed a nuclear weapons program that poses a growing danger to Japan. The North Koreans have successfully tested nuclear explosives and are believed to possess as many as 60 bombs. They have also test-fired ballistic missiles with ranges sufficient to strike the Japanese islands.

In response, Japan has deployed ballistic missile defense systems to shoot down incoming rockets; but the more bombs North Korea can use in an attack the less likely it becomes that the defensive systems can prevent a nuclear explosive from striking Japanese territory and inflicting horrific damage. The Japanese have therefore begun to debate whether successfully preventing a North Korean attack requires not only a defense against it but also the capacity to retaliate against North Korea itself or even to launch a preemptive attack. The stable deterrence of war during the Cold War, after all, rested on the ability of both the United States and the Soviet Union to retaliate against the other in response to an attack. Retaliation or preemption would in turn require the kinds of ballistic missiles that Japan could certainly develop but currently lacks.

The Japanese-American Security Treaty commits the United States to defend Japan, and it is American military forces that have deterred North Korea. If and when North Korean nuclear-tipped missiles can reach the United States, however, the Japanese will have to decide whether American deterrence will remain credible and therefore effective. For in that case a conflict involving North Korea in which the United States becomes involved might prompt the communist regime in Pyongyang to launch a nuclear attack on North America; and the prospect of such an attack might weaken the American resolve to defend its Japanese ally. Moreover, the Japanese, like other American allies, are already nervous about the willingness of the United States defend them because of the statements of the current American president questioning the value of America’s overseas commitments. With the North Korean nuclear threat growing and American protection uncertain, a serious discussion about acquiring nuclear weapons for the purpose of checking the communist regime in Pyongyang will be difficult for Japan to avoid.

China, too, poses a threat to Japan—in important ways an even more serious threat than does North Korea. As its economy has grown, Beijing’s ambitions to dominate East Asia, supplanting the United States as the major military power there, have similarly expanded. As well as possessing nuclear weapons, China’s communist government has invested in more numerous and more advanced military hardware, which has given the country an already formidable and still-growing navy.

Both China and Japan claim ownership of eight small, uninhabited, Japanese-controlled islands known as the Senkakus (they are called the Diaoyu by the Chinese), which are located in the East China Sea roughly halfway between the two countries. In recent years China has increased its maritime presence in the waters surrounding them, leading to fears that the Chinese navy might one day try forcibly to seize them. In such an eventuality, as with North Korea, Japan would have to depend on the United States for military support; but as in the Korean case, the combination of increasing Chinese military power and doubts about American reliability lead to the question of how Japan could supplement, if not replace entirely, American military might.

Japan has begun to cooperate militarily with other Asian countries that share its concerns about China, but such ties will not provide a full-fledged substitute for the American alliance. As a rich country that had, in the 1930s and 1940s, a powerful navy, Japan could certainly amass naval forces on a par with those that China deploys; but the necessary buildup would take a large financial commitment and years to accomplish. In 2018-2019 China spent $175 billion on its military while Japan’s total defense spending was $47 billion. The quickest, cheapest, and technologically most feasible way for Japan to offset Chinese power would be to acquire nuclear weapons.

The great English economist John Maynard Keynes, criticized for having altered his opinion on an economic matter, is supposed to have relied, “When the facts change, I change my mind. What do you do, sir?” While the people and the government of Japan remain viscerally opposed to the acquisition of nuclear weapons, the facts of international life in Northeast Asia are changing rapidly; and these changes may force the Japanese, on this issue, with great reluctance, to change their minds.