How Japan's Southwest Shift Is Building an 'Island Shield'

Under the Sanae Takaichi government, Japan is rapidly retooling its deterrence. On March 31, Tokyo, for the first time, deployed domestically produced long-range counterstrike missiles in Kumamoto, while introducing Hyper Velocity Gliding Projectiles in Shizuoka. These systems are designed to defend, and if necessary, strike an imminent threat at range.

In the coming year, the Defense Ministry plans to extend similar deployments across the southwest, stitching together a more resilient missile defense network along the archipelago's exposed edge.

But the latest shift reflects more than hardware. As defense spending climbs, Japan is quietly shedding old constraints and recalibrating its forces for a harsher strategic climate, one largely defined by China's growing naval presence.

To unpack this "Southwest shift" and what it reveals about the nation's evolving defense posture, Japan Forward spoke with a series of experts. In Part I, we sit down with Maki Nakagawa of the Japan Institute for National Fundamentals, a former commander in the Ground Self-Defense Force's intelligence unit.

Excerpts of the interview follow.

How is Japan's Southwest pivot reshaping its security and deterrence posture?

The upgraded Type-12 long-range surface-to-ship missiles have a range of approximately 1,000 kilometers — a substantial increase from their previous 200-kilometer reach. 

Even from Kyushu, it places key strategic locations such as Shanghai, home to the major Chinese Naval base in the Eastern Theater Command, within range. In the event of a contingency, deployment to the Southwest Islands would further extend its reach to encompass naval bases along Taiwan's opposite coast, as well as Chinese amphibious assault ships crossing the strait and the destroyers escorting them. 

By fiscal year 2030, the GSDF also plans to deploy the Type 03 Medium-Range Surface-to-Air Missile to Yonaguni, located just 110 kilometers (70 miles) from Taiwan. While the island already hosts coastal surveillance units, a new air-defense electronic warfare unit is scheduled to be established by fiscal year 2026. This will further solidify Yonaguni's role as a key hub for intelligence gathering and electronic warfare in the Southwest Islands. 

The systems would serve as a meaningful deterrent against a potential Chinese invasion of Taiwan.

Will the latest developments affect Beijing's strategic calculus?

While deterrence is difficult to quantify, it undoubtedly factors into China's operational planning. For instance, it remains unclear whether mines have actually been laid in the Strait of Hormuz, yet the waterway is effectively closed. The mere possibility of having to respond to such a scenario can itself create psychological hesitation.

Japan's shift toward strengthening its presence in the Southwest Islands alone is unlikely to alter China’s strategic calculus. However, it can raise the threshold for decision-making. 

At the same time, it is essential to recognize that China may seek to neutralize these deterrent capabilities if they are perceived as obstacles to its operations. This highlights the need for increased protective measures for Japan, including the development of hardened shelters and other defensive infrastructure.

Amid increasing Chinese activity, which areas should Japan focus on to reinforce its air and maritime defenses?

While Japan has recently begun to address gaps in its southwest, a significant vacuum remains along the Pacific side near the Second Island Chain. 

In recent years, Chinese naval activity around Japan's remote Pacific islands has become increasingly routine. Yet Japan's Air Defense Identification Zone (ADIZ) currently extends only as far as Kita-Daito Island and does not cover the airspace over the Ogasawara Islands and beyond. 

Although reports suggest the government is considering expanding the ADIZ, Japan should accelerate efforts to develop bases on Iwo Jima and Minamitorishima and establish a comprehensive air defense network along its Pacific flank.

At the same time, the nature of warfare itself is evolving. Drawing lessons from Russia's invasion of Ukraine, Japan's Ministry of Defense has identified key capability gaps. Yet unless equipment development and procurement, force deployment, and training are carried out with urgency, such capabilities will already be outdated by the time they are operational. 

Moreover, success in these emerging domains will depend not only on military innovation but also on leveraging civilian technologies. This will require sustained investment and close cooperation with the private sector.

With the Iran conflict prolonged, how might China potentially leverage the situation?

China has consistently sought to exploit power vacuums in Northeast Asia. From a military standpoint, any shift of US forces toward the Middle East works to Beijing's advantage.

Since the start of the second Trump administration, Japan has faced growing expectations to strengthen its autonomous defense capabilities. Moments like these underscore the need for a thorough examination of what Japan can — and should — do independently. 

In the context of a Taiwan contingency, current discussions largely center on how Japan would support US forces. Yet an equally critical question remains: what would Japan do if the US chose not to intervene?

Establishing a shared understanding of Taiwan's geopolitical importance to Japan, while rigorously considering a range of contingencies, will be essential for shaping a credible and resilient security strategy.

What level of autonomous defense capability should Japan aim for, and how should this be balanced with the Japan-US alliance?

The level of capability required is inherently fluid, as it depends on the relative balance of forces. That said, one area where Japan's current posture is clearly lacking is nuclear capability. 

Revisiting the Three Non-Nuclear Principles should not be equated automatically with Japan pursuing its own nuclear arsenal. Rather, the debate should encompass a range of options, including whether to pursue a NATO-style nuclear sharing arrangement, how such a framework might be adapted to the Japan-US alliance, and whether the immense costs and time required for an indigenous nuclear capability would yield meaningful strategic benefits. 

If the objective is to ensure that Japan never again suffers nuclear devastation, then these questions warrant open and rigorous debate.

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• China's Maritime Militia Is a Growing Threat 

Author: Kenji Yoshida