Earlier this month, North Korea launched four ballistic missiles toward Japan. Three of them landed within Japan’s exclusive economic zone, less than 200 miles from the country’s coast, in an area frequented by Japanese fishing boats. The missile test, North Korean state media claimed, was aimed at “the bases of the U.S. imperialist aggressor forces in Japan.” By demonstrating that it could carry out a so-called saturation attack—one in which a massive barrage of missiles would overwhelm Japan’s defenses—Pyongyang sought to weaken the credibility of the military deterrent that Japan, the United States, and South Korea have erected against it.

North Korea has conducted dozens of missile tests and three nuclear tests since Kim Jong Un took office in late 2011. Over the same period, Pyongyang’s missile capabilities have grown and its arsenal’s vulnerability to attack has diminished.

Last August, North Korea successfully tested a submarine-launched ballistic missile. In February, it tested an intermediate-range ballistic missile propelled by solid fuel—a technological leap that would allow Pyongyang to dramatically reduce the signs of an impending launch, helping to insulate its missiles from preemptive strikes. The Kim regime is now attempting to create a nuclear warhead small enough to attach to the tip of a missile, a step toward its ultimate goal of creating an intercontinental ballistic missile that could deliver a nuclear bomb to the continental United States. Through an elaborate shell game involving mobile missile launchers and the diversification of its launch sites, North Korea has sought to sow doubts in the United States, Japan, and South Korea about the potential efficacy of preemptive action.

All of these developments have worried Japanese policymakers, deepening a long-standing debate in Tokyo over the country’s security posture. At issue is whether enhancing Japan’s missile defense capabilities will be enough to meet the threat and whether Tokyo should equip itself for a preemptive strike against North Korea—a move that could raise China’s ire and create domestic controversy due to Japan’s own constitutional constraints.

Japanese Prime Minister Shinzo Abe in the Diet after reports of a North Korean missile test, Tokyo, March 2017.
Japanese Prime Minister Shinzo Abe in the Diet after reports of a North Korean missile test, Tokyo, March 2017.
Issei Kato / REUTERS


Japan’s current defense against North Korean missiles is based on a two-tiered system. In the Sea of Japan, Japanese destroyers equipped with the Aegis missile defense system serve as the country’s frontline interceptors. Land-based Patriot Advanced Capability-3 (PAC-3) batteries provide a second layer of protection. This system is effective in some respects, but it is becoming increasingly insufficient in light of the North’s expanding capabilities—especially its potential capacity for a saturation attack in which multiple missiles would be launched at different targets.

As Japan’s strategic position has deteriorated, Japanese policymakers’ interest in new military capabilities has grown, placing a long-standing technocratic debate over how to respond to the North Korean threat at the center of the country’s politics. On the same day as Pyongyang’s missile test, Japanese Prime Minister Shinzo Abe told the Diet that the threat posed by North Korea had reached a “new stage.” A day later, Itsunori Onodera—the chair of the ruling Liberal Democratic Party’s committee dealing with the North Korean missile threat and a former defense minister—underscored the need for Japan to start considering offensive options. “If bombers attacked us or warships bombarded us, we would fire back,” he told Reuters. “Striking a country lobbing missiles at us is no different.” (Many opposition politicians, such as Akihisa Nagashima, a key Democratic Party member of the Diet and a former vice-minister of defense, agree that Japan’s defense posture is in need of reform, though the nature of the changes is contentious.)

Japan’s constitution does not necessarily prohibit the country from carrying out a preemptive strike.

In the coming months, the Liberal Democratic Party will present a report to the government outlining Japan’s options for dealing with the North Korean threat. Tokyo has already committed $1 billion to upgrading its PAC-3 interceptors, and it is also considering deploying land-based Aegis systems to complement its sea-based capabilities. In February, Japan conducted a successful joint test with the United States of the Standard Missile-3 Block IIA system—a missile interceptor tied to the Aegis system that, if deployed in Japan, would improve the country’s missile defenses both on land and at sea.

Many in Tokyo are now considering adding a third layer to Japan’s missile defenses by asking Washington to deploy the Terminal High Altitude Area Defense (THAAD) system to Japan. THAAD’s sophisticated radar and its ability to destroy incoming projectiles at a high altitude would reduce the leakage produced by intercepted missiles, limiting the damage that their debris would cause in populated areas—an advantage that would be even more valuable in the event of a nuclear attack. (The United States is currently deploying THAAD to South Korea, in a move that China has opposed.)

Such measures would be useful, but they might not be enough to deter a North Korean attack or to withstand a particularly sophisticated one. That is why Japanese policymakers are also debating acquiring weapons that would allow their country to destroy North Korean missiles before they are launched, perhaps in conjunction with the United States—a capability that Japan now lacks. Japan could buy Tomahawk missiles from the United States, for example, or it could use the F-35A fighter, which Japan is slated to procure in the coming years, to strike North Korean targets. Precision guided missiles, such as Lockheed Martin’s Joint Air-to-Surface Standoff Missile, are another option. The best choices among these preemptive options are those pieces that would work well with Japan’s destroyers in the Sea of Japan, such as the F35A and Tomahawk cruise missiles.

People watch a news report on a North Korean missile test at a train station in Seoul, South Korea, February 2017.
People watch a news report on a North Korean missile test at a train station in Seoul, South Korea, February 2017.
Kim Hong-Ji / REUTERS


The debate over whether to acquire these kinds of weapons will probably intensify in the coming months if North Korea steps up its provocations. That will likely complicate the debate over revising Japan’s pacifist constitution, which has kept Tokyo from maintaining a traditional military since the end of World War II. It has also prohibited Japan from procuring offensive weapons systems, such as intercontinental ballistic missiles and long-range strategic bombers, which would exceed the minimum level of force needed for the country’s self-defense. The document has been a lightning rod for criticism from conservatives who claim that it is overly prohibitive. Revising it appears to be one of Abe’s major goals; whether he will be able to do so before he leaves office is unclear. Time running out is not as much of an issue as it was before: Abe could theoretically remain in office until 2021, thanks to a change in the LDP’s rules, which now permit a third term for the party’s leader.

Even in its current form, however, Japan’s constitution does not necessarily prohibit the country from carrying out a preemptive strike against a threat from North Korea. The constitution may permit preemptive actions when they are the only way to safeguard Japan’s security against an imminent danger and when they are carried out with a proportional amount of force. What’s more, although the prevailing interpretation of the constitution places the overseas deployment of Japanese forces with the aim of using force beyond the limits of self-defense, it does not explicitly rule out striking overseas targets using equipment based in Japan. This leaves the door open for lawmakers and lawyers to justify using preemptive weapons. In any case, the procurement and deployment of weapons such as cruise missiles would not in itself need to fulfill the constitution’s requirements for the use of force.

But there are challenges to gaining preemptive strike capabilities that go beyond the constitution. First, it’s not clear whether such capabilities—even when combined with a U.S.-led surgical strike—would be able to neutralize Pyongyang’s missile programs, which are being developed to withstand preemptive attacks. Second, the costs associated with such a strike, which would probably include retaliatory actions by North Korea against Japan and South Korea, may outweigh the benefits. And finally, Japan’s development of preemptive capabilities would raise eyebrows among pacifists in Japan and among officials elsewhere in the region—especially in China—and help feed into false narratives about Japan’s alleged remilitarization. Beijing would also likely protest the deployment of THAAD or other missile defense systems to Japan. Even though these arguments from China would ring hollow in light of Beijing’s own ability to strike Japan, it will be hard for Tokyo to bolster its national security without exacerbating broader tensions in northeast Asia. Japanese officials and their allies in South Korea and the United States should continue to publicly discuss their options anyway, if only to signal to Pyongyang that its escalations will not be met with silence.

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  • J. BERKSHIRE MILLER is a Tokyo-based International Affairs Fellow at the Council on Foreign Relations and a Senior Fellow on East Asia at the EastWest Institute.
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