Japan's Defense Transformation Is More Ambitious Than It Looks

Three years after Japan released its landmark security documents in December 2022, the strategic picture looks considerably different from the one those papers described. The concept of "counterstrike capability"—which Tokyo used to justify acquiring long-range strike weapons—has quietly given way to something broader and arguably more honest about what Japan is actually building toward. 

Ken Jimbo, one of Japan's most prominent security scholars, sat down with Japan Forward to assess how far the country has come, and how far it still has to go.

Japan's Evolving Threat

The 2022 National Security Strategy and National Defense Strategy positioned counterstrike capability as part of Japan’s broader missile defense and stand-off defense posture: a minimum self-defense measure to be used when an armed attack against Japan has occurred or is judged to be underway, and when no other means are available to defend the country.

Jimbo suggests that the deliberate ambiguity was the result of efforts to "construct a rationale for enabling ground-attack capabilities." The reasoning was constructed around how to enable ground-attack capability," he says. But the strategic environment has shifted faster than the doctrine.

Today, the primary driver of Japan's long-range strike posture is not North Korean ballistic missiles but Chinese naval power. As China's missile forces, naval assets, and air power project further eastward, Japan finds itself potentially within range of precision-guided munitions across its entire territory. In that context, the focus has moved from land-attack scenarios to maritime strike—hitting Chinese naval assets before they can establish sea control. "The main subject of advanced stand-off defense has become attacks on maritime assets," Jimbo says flatly.

This evolution, he acknowledges, has not been well explained to the public. Japan's defense establishment has been faster at acquiring capabilities than at articulating their rationale.

The Missile Gap the Alliance Has Yet to Solve

One structural problem that remains unresolved is what analysts call the "missile gap" imbalance. China possesses more than 2,000 short-and medium-range strike missiles. Offsetting that arsenal with equivalent forward-deployed forces in the western Pacific is, in Jimbo's words, "extremely difficult"—partly because the United States lacks suitable basing sites on Pacific islands, and partly because Washington constrained itself through the Cold War-era Intermediate-Range Nuclear Forces Treaty, which prevented it from deploying such missiles in the first place.

Japan's own buildup does not directly fill this gap. "Basically, this depends on how the United States positions its medium-range missiles in the Indo-Pacific theater," Jimbo says. The question of who closes the gap—Tokyo, Washington, or a joint structure—remains open.

The Unfinished Agenda

Looking ahead to Japan's next security strategy review, covering 2026 to 2030, Jimbo points to two areas where the 2022 documents left significant work undone.

The first is responsiveness. Japan has invested in moving forces southwestward toward the Nansei island chain, but those forces need to be able to deploy under fire, not just in peacetime. "You need highly survivable means of movement," Jimbo says, "and you have to take an integrated operations approach that ensures sea and air superiority during the movement." Without that, rapid reinforcement remains more aspiration than capability.

The second gap is sustainability. Modern warfare consumes ammunition at rates that can exhaust stockpiles within days. Jimbo argues that "magazine depth"—the ability to keep the front line supplied—depends not just on what is stored but on how quickly it can be replenished through domestic production. 

Japan has begun grappling with wartime industrial capacity, but joint production arrangements with allies remain embryonic. Interoperable co-production of munitions, which would not require sharing the most sensitive technologies, is technically feasible but has yet to be institutionalized. "We still have to build those schemes one by one," he says.

Rethinking the Alliance

Perhaps the most searching part of Jimbo's analysis concerns the Japan-US alliance itself. Washington has praised Tokyo's defense buildup, and the March 2026 Takaichi-Trump summit yielded agreements on joint missile development and production. 

But Jimbo draws a clear line between procurement cooperation and extended deterrence. The former is achievable through contracts and joint programs; the latter requires the United States to commit to intervening in a crisis—a commitment that, in the current political climate, cannot be taken for granted.

His prescription is not to abandon the alliance but to make it structurally harder to abandon. "Japan needs to create conditions under which, when America considers how to respond to a crisis, the Japan-US alliance is naturally taken as the default," he says. That means interoperable forces, robust joint exercises, and a demonstrable Japanese willingness to fight—not as a form of burden-sharing, but as the operating system of the alliance itself.

Deterrence by Denial

Asked directly whether Japan's strategy is shifting from deterrence to denial—raising the cost of aggression rather than threatening punishment—Jimbo does not hesitate. "Denial," he says. Numerical parity with China is neither achievable nor the goal. What Japan can credibly aim for is denying Beijing the ability to achieve its operational objectives: seizing the Senkakus, controlling Taiwan's straits, establishing fait accompli in the western Pacific.

"If we can deny the enemy's ability to execute its operations, deterrence by denial is established," he says. That is the animating logic of Japan's defense transformation—less about matching China missile for missile, and more about making the first move too costly to complete.

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Author: Daniel Manning