Rearmament of Iwo Jima and the Development of Counterattack Capability: A Turning Point in Japan's Post-War Security Policy

In March 2026, a convoy of transport vehicles quietly departed before dawn towards the Ground Self-Defense Force's Kengun Base in Kumamoto Prefecture. Onboard were the launch units of the improved Type 12 Surface-to-Ship Missile, commonly known as the "Type 12 SSM-ER," developed by Mitsubishi Heavy Industries. This deployment marks a historic turning point, as it grants Japan's operational forces the capability to strike threatening targets beyond its own territory for the first time since World War II.

Since the formal introduction of the concept of "counterstrike capability" in the revised "National Security Strategy" in December 2022, Japan's defense policy has undergone fundamental changes. The traditional division of roles in the Japan-U.S. alliance—where Japan serves as the "shield" with a strictly defensive posture, and the U.S. maintains offensive capabilities as the "spear"—is now rapidly eroding. The Type 12 SSM-ER, with a range of approximately 1,000 kilometers, can target major military facilities along the Chinese coast and strategic sites in North Korea when operated from Kyushu and the southwestern islands. This is not merely an enhancement of weapon performance; it signifies an expansion of Japan's strategic autonomy.

According to the Ministry of Defense, the defense budget for fiscal year 2026 is expected to reach approximately 9 trillion yen, setting a new post-war record. The acquisition cost for the Type 12 SSM-ER alone is estimated at around 177 billion yen (approximately 1.13 billion dollars), and when combined with additional procurement of Tomahawk cruise missiles and development costs for the next-generation fighter (F-X), Japan can be evaluated as having seriously embarked on building a "proactive deterrent capability." The U.S. Department of Defense's "Military Power of China Report," published in December 2025, states that the People's Liberation Army's long-range precision strike capabilities have reached 2,800 to 3,700 kilometers, placing U.S. military bases, including those in Okinawa and Guam, under threat, and this reality is driving Japan's policy shift.

Simultaneously, there is a strengthening of the defense posture in the Pacific region. The Ministry of Defense is currently considering a significant expansion of military infrastructure on Iwo Jima, located about 1,200 kilometers south of Tokyo. Specifically, plans are being discussed to extend the existing runway, enhance port facilities, and install floating piers capable of accommodating large supply ships. Furthermore, there are plans to permanently deploy Air Self-Defense Force fighter jets to establish a system that can quickly respond to foreign aircraft and vessels approaching the eastern waters.

The strategic importance of Iwo Jima is clearly derived from its geographical position. It is the only island in the Pacific theater with a runway capable of operating Self-Defense Force fighter jets, and it is increasingly being positioned by defense planners as a key element of "strategic redundancy" in case bases in Okinawa or Yonaguni become incapacitated due to a Chinese preemptive strike. In terms of cooperation with the U.S. military, strengthening the Self-Defense Force's presence on Iwo Jima provides both countries with options for mobile defense that are not constrained by the inner side of the first island chain. According to a report by Naval News in December 2025, the Ministry of Defense plans to begin next fiscal year the development of fuel and ammunition supply systems and feasibility studies for port infrastructure on the island.

This series of developments will have complex implications for the security architecture in Northeast Asia. In a summit meeting with President Trump on March 19, Prime Minister Sanae Takaichi reaffirmed the strength of the Japan-U.S. alliance and hinted at the possibility of mine-clearing support in the Strait of Hormuz. This suggests that Japan's mine-clearing capabilities, developed over years of anti-piracy operations in the Gulf of Aden, may be drawn into the context of strategic engagement in the Middle East, which is noteworthy in terms of Japan's geographical expansion of security commitments.

However, the expansion of capabilities does not automatically guarantee the success of deterrence. The deployment of the Type 12 SSM-ER and the fortification of Iwo Jima may be perceived from Beijing as a signal that Japan is "shifting towards an aggressive posture," which carries the risk of provoking a response from China. Even after entering 2026, the Chinese Navy's aircraft carrier forces continue to operate east of the first island chain, and concerns regarding underwater survey activities remain. The structure in which these Chinese actions serve as justification for Japan's policy shift presents a typical security dilemma.

Relations with South Korea also function as a variable. As Japan possesses counterstrike capabilities and advances the deployment of forces to Iwo Jima, Seoul must prioritize addressing the nuclear and missile threats from North Korea while also conducting its own assessment of Japan's expanding military role in Northeast Asia. While Japan-South Korea defense cooperation has shown improvement in recent years, the risk of historical issues reigniting remains ever-present, and there continues to be a political ceiling on the deepening of trilateral (Japan-U.S.-South Korea) security cooperation.

I would like to be cautious in declaring this shift as the "end of the post-war security system." It is true that Japan still adheres to the fundamental principle of exclusively defensive posture and imposes strict political and legal requirements on the exercise of counterstrike capabilities. However, when considering the three realities of a 9 trillion yen defense budget, the operational deployment of a 1,000-kilometer range surface-to-ship missile, and the fortification of Iwo Jima as a Pacific defense base, it is undeniable that this signifies a transition from a "shield nation" to a "proactive deterrent player." The security environment in Northeast Asia is likely to undergo even more fundamental transformations in the coming years.

(Main sources: Asia Times, March 2026; Naval News, December 2025; U.S. Department of Defense "Military Power of China Report 2025"; UPI, March 29, 2026; Christian Science Monitor, March 20, 2026)