By JNP Col. Yoshimasa Adachi, PhD
The Japanese Ministry of Defense established the Pacific Defense Architecture Office on April 1, 2026, underscoring Japan’s intention to strengthen its defensive posture in the Pacific region. Until recently, Japan’s security policy primarily focusedon countering North Korean missile threats and responding to China’s activities in the waters surrounding the Southwest Islands. Accordingly, defense efforts emphasized the development of radar installations and related infrastructure along the Sea of Japanand East China Sea fronts. In recent years, however, China has expanded its influence beyond Japan’s island chain into the Pacific Ocean, while significantly intensifying its military activities in that area.
In June of last year, two Chinese aircraft carriers were deployed simultaneously to the Pacific Ocean for the first time, conducting approximately 1,000 aircraft takeoff and landing exercises. This deployment marked the first instance in which a Chinese aircraftcarrier advanced east of the so‑called Second Island Chain—a strategic line connecting the Izu Islands, the Ogasawara Islands, Guam, Saipan, and Papua New Guinea, which China regards as part of its military defense perimeter. Furthermore, these carriergroups operated within Japan’s exclusive economic zone (EEZ), approximately 300 kilometers southwest of Minamitorishima, Japan’s easternmost territory. This EEZ is believed to contain at least 16 million tons of rare earth elements and has gained strategicimportance following Japan’s successful exploratory drilling of rare‑earth‑bearing seabed mud conducted in January and February of this year.
As China’s military activities in the Pacific have intensified, views have grown within the Japanese government that its intelligence‑gathering and surveillance capabilities in the Pacific remain insufficient and that a strengthening of defensive measures isnecessary. In response, the government plans to revise Japan’s three core security documents—the National Security Strategy, the National Defense Strategy, and the Defense Buildup Program—within the year, and intends to position the strengthening of Pacific defense as one of its central policy objectives.
As a concrete measure, the deployment of a mobile air traffic control radar to Kita‑Daito Island, located approximately 360 kilometers east of Okinawa Island in the Pacific Ocean, is expected to be accelerated. This mobile early‑warning and control radar willsupplement the network of 28 fixed radar sites deployed nationwide. Employing phased‑array radar technology—the same system used aboard Aegis‑equipped destroyers—it enables continuous, 360‑degree surveillance.
In addition, Japan will begin surveys this year for the development of port facilities on Iwo Jima. Situated along the Second Island Chain, Iwo Jima occupies a strategically important location roughly midway between the Izu Islands and Guam, a major U.S. military base, and hosts a permanent unit of the Japanese Self‑Defense Forces. The island’s coastline is characterizedby shallow waters, preventing the docking of large vessels; accordingly, new piers will be constructed to enhance the Self‑Defense Forces’ transport and logistical capabilities.
Iwo Jima also possesses the distinctive advantage of being located more than 2,000 kilometers from the Chinese mainland. China maintains approximately 1,000 short‑range ballistic missiles with ranges of 600 to 850 kilometers, covering Taiwan and Japan’s southwesternislands. Taking advantage of Iwo Jima’s relative location outside the effective range of these missiles, plans are underway to construct a full‑scale runway to ensure the stable operation of fighter jets.
Furthermore, proposals are underway to expand the existing runway on Minamitorishima Island, alongside plans to develop a firing range for long‑range surface‑to‑ship guided missiles. These domestically produced missiles have a range exceeding 1,000 kilometers—morethan five times that of conventional systems—and are expected to form the backbone of Japan’s long‑range stand‑off missile capability, which can be employed from outside an adversary’s engagement range. With these developments, Japan’s stated objective of acquiring counterattack capabilities has entered the operational phase, and plans are in place to furtherexpand the deployment of similar missile systems.
During his visit to Iwo Jima in March of this year, Defense Minister Koizumi stated that “strengthening the defense system across the vast sea and airspace on the Pacific side is an urgent issue. The current posture is not necessarily sufficient, and wide areason the Pacific side remain in a state of defense vacuum.” The newly established Pacific Defense Architecture Office is expected to serve as a driving force behind efforts to strengthen Japan’s defensive posture in the Pacific region.
Meanwhile, the Chinese military is accelerating efforts to establish an anti‑access/area denial (A2/AD) strategy aimed at preventing the intervention of U.S. forces in the event of an armed conflict over Taiwan or other regional contingencies. According toJapan’s Ministry of Defense, the Chinese military exercises conducted in June of last year—referenced earlier—simulated operations against a U.S. carrier strike group, with one Chinese aircraft carrier reportedly designated to play the role of a mock U.S.carrier.
At the same time, it is becoming increasingly difficult for the United States military alone to counter the expanding scale and modernization of China’s armed forces and to dismantle China’s A2/AD posture. In its National Security Strategy released last December, the United States stated its intention to build a military capable of deterring aggression in the Taiwan Strait and across the entire First Island Chain—stretching from Kyushu and Okinawa through Taiwan, the Philippines, and Borneo—while candidly acknowledging that this objective cannot be achieved by the United States alone.
Compounding this challenge, instability in the Middle East, particularly the situation in Iran, raises the possibility of U.S. force redeployments and ammunition depletion, which could weaken American deterrence in the Indo‑Pacific. Under these circumstances,cooperation from U.S. allies, including Japan, has become indispensable. Japan’s efforts to strengthen Pacific defense through the deployment of radar systems and the development of port infrastructure by the Self‑Defense Forces will complement U.S. militarycapabilities and contribute significantly to enhancing the overall deterrence of the Japan–U.S. alliance.
