Is Japan’s Interest in Strike Capabilities a Good Idea?


In the span of a month, Tokyo has rapidly gone from canceling a ballistic missile defense system to considering strike capabilities against foreign adversaries. Is Japan on the precipice of dramatically changing the way it uses its military?

In early June, Japanese Defense Minister Tarō Kōno announced Japan would suspend its planned deployment of the Aegis Ashore ballistic missile defense system, surprising many in both Tokyo and Washington. Kōno said the government feared the boosters of the interceptors would hit local communities after they separated from the interceptors. While there are questions whether the interceptor issue was the real reason behind the cancellation, Kōno said that the necessary software modifications to correct the problem have not been successful thus far, making a hardware redesign likely necessary to solve the problem. The redesign was projected to cost $1.8 billion and take roughly a decade to implement, a cost and timeline that Tokyo found unacceptable, leading Japan’s National Security Council to agree to cancel the program.



In the short time since Kōno’s announcement, the situation has become more confusing. While Acting Assistant Secretary of Defense David Helvey has stated publicly that the United States intends to continue talks with Japan to move forward with deployment of the Aegis Ashore system, Tokyo has broadened the discussion to ways to strengthen Japan’s deterrence capabilities that include what it calls “enemy base attack,” a euphemism for strike capability, which Japan has eschewed since its defeat in World War II.

Unplanned and not part of any broader strategic dialogue among allies, Japan’s suspension of Aegis Ashore has nevertheless opened a broader discussion over what kind of military Japan wants to have and what kind of roles Japan is prepared to perform. Because this debate has the potential to reshape Japan, the alliance, and broader regional relations, Tokyo can expect to face several challenging issues including altered alliance relations, cost and technological considerations, feasibility, and important legal questions.

Effects on the United States-Japan Alliance

Designed primarily to deal with North Korean threats, Japan’s ballistic missile defense system consists of two layers. The Japanese Maritime Self-Defense Force operates the sea-based tier from its Aegis-equipped destroyers. Currently there are seven destroyers, with an eighth and final one expected in the near future. These destroyers are fitted with Standard Missile-3 interceptor variants that target incoming ballistic missiles in their mid-course phase. The second tier consists of ground-based fire units operated by the Air Self-Defense Force that use the Patriot Advanced Capability-3 interceptor. Seen as a way to augment the sea-based tier, these missiles are intended to intercept missiles in their terminal phase if they should penetrate the sea-based tier. Japan viewed the Aegis Ashore units as a way to supplement the Aegis-equipped ships, particularly because weather or maintenance issues could mean lags in coverage should these ships be forced into port.

While Aegis Ashore is primarily for Japan’s defense and the choice to suspend it is Tokyo’s to make, underemphasized in Japan’s public debate is the negative effect its absence will have on the U.S.-Japan alliance. The United States would have benefited from Japan’s Aegis Ashore system. In addition to improving Japan’s capability and capacity to protect U.S. forces stationed in Japan, Aegis Ashore would have enhanced U.S. homeland defense capabilities. Importantly, U.S. military operators saw Aegis Ashore as a way to free up American Aegis destroyers in the region to shift to other areas where China is active, such as the South China Sea, Indian Ocean, and Philippine Sea. Seen from this perspective, Japan’s deployment of Aegis Ashore would complement U.S. regional strategy. Its cancellation, therefore, complicates America’s approach to the region. For example, Adm. Harry Harris, then-commander of U.S. Pacific Command, told Congress in 2018 that without Japan’s Aegis Ashore deployment, the U.S. Navy would have limited flexibility to take its Aegis-equipped destroyers that are defending Japan and put them elsewhere because of U.S. treaty obligations to defend Japan.

This is not to suggest that Aegis Ashore would meet all of Japan’s security challenges. There are legitimate questions regarding the cost-effectiveness of devoting billions of dollars to a single system that may or may not succeed in intercepting incoming ballistic missiles. Moreover, Japan’s Aegis Ashore was limited to ballistic missiles despite initial considerations that included capabilities to defend against both ballistic and cruise missiles (which were scrapped due to cost concerns). Given China’s existing inventory of cruise missiles and progress on hypersonic boost-glide missiles, however, even Japan’s planned Aegis Ashore sites would not have protected against all potential missile threats.

From Missile Defense to Strikes

Instead of searching for alternative ways to strengthen the nation’s missile defense systems, Japan moved the conversation to enemy base attack capabilities. While it may be a major leap in logic to move from a defensive Aegis Ashore system to an offensive capability to attack enemy bases, this discussion of the capability is not new. In March 2017, the governing Liberal Democratic Party examined the issue but ultimately did not act upon it. After the Aegis Ashore suspension, however, this topic was revived under the broader issue of Japan’s deterrence capabilities. The government has argued that it needs to consider a capability to strike an enemy base with missiles before the enemy can launch as a means to strengthen Japan’s deterrent capabilities. Japan is not seeking a full denial capability that can hold adversaries at bay and threaten to completely neutralize the adversary’s missiles. Rather, Tokyo is looking at how a limited number of strike capabilities can augment the existing ballistic missile defense system to deter adversaries from launching attacks on Japan. The logic is to do enough to complicate enemy planning and hope it reduces the enemy’s willingness to strike. But if the adversary does decide to strike, the goal is to minimize as many incoming missiles as possible before they are launched and knock out the surviving ones in the air.

Beyond this conceptual framework, however, it is not entirely clear what Tokyo is intending to do. Japan is already procuring cruise missiles designed for jet fighters with 500- to 900-kilometer ranges that government officials believe can be used in a capacity to strike enemy forces far from Japanese shores (e.g., JASSM-ER). Japan’s fleet of aerial refuelers and growing number of F-35s help extend the ranges of these missiles even further. Additionally, Japan is developing ground-launched hyper-velocity gliding projectiles that, depending on their range and location, would be able to reach North Korea and even parts of China. What exactly then are officials referring to when they are discussing enemy base strike capabilities? Are they considering extending the ranges of the capabilities they already plan to procure? Is the Aegis Ashore cancellation an opening for hosting U.S. ground-based intermediate range missiles that were prohibited under the Intermediate-Range Nuclear Forces Treaty or, at the very least, procuring and operating their own ground-based, intermediate-range missiles?

Moreover, if the disqualifying factors in the Aegis Ashore deployment were the costs and time required to make the changes, it is unclear whether the acquisition of strike capabilities would fare any better. After all, acquiring time-sensitive target strike capabilities will require Japan to develop or procure a new mix of missiles in addition to the supporting infrastructure that is required to find, fix, track, and target what are likely to be mobile and well-hidden targets. It will also require robust cyber, space, and electromagnetic capabilities to degrade an adversary’s defenses before Japan’s missiles are even launched. All of this is likely to be costly and take time to develop or acquire and perfect, even if it is done in close cooperation with the United States.

And it is not clear that all the effort will be worth it. Hunting adversary transporter erector launchers (a type of mobile launcher used for transporting and launching a missile) is difficult, particularly with adversaries that have many mountains and places to hide their launchers. In 1991, the United States had air superiority over Western Iraq, had special operations forces on the ground, and the Iraqis were operating in comparatively open terrain, and yet, despite all of these advantages, there is no proof that the coalition successfully destroyed a single Iraqi launcher. Does Japan think it will face better odds in China or North Korea?

There is also a question of whether this is good for the alliance. While the United States has shown a willingness to support a more forward-leaning Japan, a move toward strike capability promises to change the nature of the alliance. The alliance has always been a shield and spear relationship, with Japan geared toward defense and the United States toward offense. If suddenly Japan also has a spear — even a small one that is limited to self-defensive purposes only — how does this change the roles and missions of the alliance? Is Japan assuming that it can skip the difficult steps of acquiring tracking and targeting capabilities by relying on U.S. intelligence? If so, does the United States have the bandwidth to support Japan’s needs? If it does, is Japan ready to reconsider current alliance command-and-control structures should U.S. cooperation require closer integration over these types of operations, or broader operational command, similar to the integrated command structure that exists in the U.S.-Korea alliance?

Uncharted Territory for the Self-Defense Forces

In addition to alliance relations, what does the decision do to regional dynamics? Japan’s acquisition of strike capability could represent a dramatic shift in Northeast Asia’s military competition. Regardless of what Japan calls its new capabilities, the region will see them as offensive weapons, particularly if the discussion focuses on preemptive use. Even if Japan argues they are designed for North Korea, China will not view it that way. Nor should it given that the public discussion in Japan has included China, and Japanese government publications, including Japan’s most recent defense white paper published earlier this week, regularly cite China as a top security threat. In this environment, China is bound to react negatively, as is North Korea, and maybe even South Korea. And if a crisis erupts, knowing Japan possesses strike capability, North Korea or China may actually have incentives to preemptively attack Japan to ensure early success.

Perhaps most fundamental of all is the fact that acquiring strike capability pushes Japan into uncharted territory. Although there is nothing illegal about Japan acquiring missiles, and the government interprets Japan’s constitutional focus on exclusive self-defense as allowing an enemy base strike if there are no other means available to avoid an attack, it still puts Japan into new territory. Short of an armed attack situation, per Japanese laws revised in 2015, whoever is sitting in the Kantei will have to decide whether activity on an adversary’s launchpad represents an imminent threat to Japan’s survival. If so, will Japan break with past precedent and launch a strike on a country with which it is not at war? Will it strike an adversary if the United States says a strike on U.S. territory is imminent in the name of collective self-defense? This is just the start of what is expected to be a legal Pandora’s box. Other questions Japan will have to face are basic operational and doctrinal questions about what should be attacked and when and how that attack should take place.

The suspension of Aegis Ashore opened a much broader discussion about what kind of military capabilities Japan wants to operate and what type of power it wants to become. This is not to say that consideration of strike capabilities is wrong. But there is a lot of homework Japan has yet to do, not least clearing up what adversary it is planning its deterrent posture around. If Japan moves forward and acquires strike capabilities, the result will be a very different Japanese defense posture and a U.S.-Japan alliance transformed from its shield-and-spear relationship into one of two spears, albeit of different lengths.



Jeffrey Hornung is a political scientist at the nonprofit, nonpartisan RAND Corporation. 


Image: U.S. Army photo