The Strategic Significance of a New Organization Facing Japan's Pacific Side Defense "Vacuum Zone"

On April 1, 2026, Japan's Ministry of Defense established the "Pacific Defense Promotion Office." Although it is a small organization with only 10 members, its strategic significance is extremely large. Defense Minister Shinjiro Koizumi stated during his inspection of Iwo Jima on March 28, "Strengthening the defense posture in the vast maritime and airspace of the Pacific is an urgent issue," and frankly acknowledged that the current capabilities are not necessarily sufficient, stating, "The extensive area on the Pacific side has effectively become a defense vacuum." This statement indicates an important turning point in Japan's security policy.

Until now, Japan's defense deployments have focused on the Sea of Japan coast to address the missile threats from North Korea and the East China Sea to counter China's maritime expansion. Specifically, plans have been made for the permanent deployment of mobile early warning control radars to Amami Oshima in Kagoshima Prefecture and to Kitadaito Island in Okinawa Prefecture, advancing the construction of a defense posture along the first island chain. However, there is a rapidly growing recognition within the Ministry of Defense that there is a significant lack of effective defense capabilities on the Pacific side, specifically in the vast maritime areas from the Izu Islands to the Ogasawara Islands and beyond the second island chain.

The background of this recognition is the rapid enhancement of the Chinese Navy's capabilities for open-ocean deployment. In June 2025, two Chinese aircraft carriers operated simultaneously in the Pacific for the first time in history, transiting through Japan's exclusive economic zone. Carrier-based aircraft conducted approximately 1,000 takeoff and landing training exercises, demonstrating practical long-range deployment capabilities that went beyond mere show of force. Notably, this was the first time that Chinese aircraft carriers advanced east of the second island chain. The second island chain extends from the Izu Islands to Guam, and Chinese naval activities beyond this line represent a direct threat to the rear support bases of U.S. forces in Japan.

The newly established Pacific Defense Promotion Office is positioned within the Ministry of Defense's Defense Capability Development Bureau and is involved in the formulation of defense capability development plans. This placement is significant. The defense capability development plan is a core document that specifies the procurement quantities and required expenses for major defense equipment over a five-year period, and incorporating the strengthening of Pacific-side defense into this plan could bring about structural changes in budget and equipment allocation. The government plans to revise the three security documents—National Security Strategy, Defense Program Guidelines, and Mid-Term Defense Capability Development Plan—by the end of 2026, with the intention of including policies for strengthening Pacific-side defense in these revisions.

An analysis report released by CSIS (Center for Strategic and International Studies) in April 2026 positions this Japanese trend within the context of the U.S.-Japan alliance. The report evaluates that the 2026 U.S. defense strategy somewhat reflects Japan's strategic priorities, such as the defense of the first island chain and deterrence against China, while also pointing out that the Trump administration's focus on the Western Hemisphere as a strategic priority and its underestimation of threats from North Korea and Russia significantly deviates from the traditional U.S. posture of treating allies only in the context of burden-sharing. This analysis supports the need for Japan to expedite its own defense capability enhancement.

Additionally, the joint exercise involving the U.S., Japan, Australia, and New Zealand, which began on April 7, 2026, and continued until April 17, included live-fire exercises, air operations, command post exercises, and large-scale maneuver exercises. This exercise aligns with the mission of the newly established Pacific Defense Promotion Office in terms of building multilateral cooperation on the Pacific side.

On the other hand, Japan is also pursuing its own diplomatic initiatives in the Middle East. Prime Minister Sanae Takaichi is coordinating a summit meeting with Iran and is also exploring a separate meeting with President Trump. Japan's stance of seeking an exit to peace in light of the blockade issue in the Strait of Hormuz is directly related to Japan's national interests from the perspective of energy security; however, the CSIS report also points out that U.S. military operations in the Middle East raise questions about the sustainability of U.S. forward deployment in the Asia-Pacific region.

The challenges facing the Pacific Defense Promotion Office are clear. Japan's Pacific side encompasses a vast exclusive economic zone extending to the Izu Islands, Ogasawara Islands, and Minami-Torishima, and the current Self-Defense Forces' posture is far from adequate to monitor and defend this area. The deployment of early warning radars, increased flight hours for patrol aircraft, the development of bases on remote islands, and, above all, the establishment of maritime surveillance capabilities east of the second island chain are required. These necessitate long-term budget measures and organizational responses, and the extent to which the new 10-member organization can drive substantial change will depend on future budget allocations and political will.

Japan's security environment has become even more complex in 2026. China's maritime expansion is crossing the first island chain and reaching the second island chain. North Korea's nuclear and missile development continues, and Russia's military activities in the Far East are also becoming more active. While the U.S.-Japan alliance is functioning relatively smoothly in operational terms, as pointed out in the CSIS report, the absence of a strategic vision poses a risk to the effectiveness of the alliance. The establishment of the Pacific Defense Promotion Office is a first step for Japan to confront this strategic vacuum, but the key to its success lies in how much concrete budget and equipment backing can be secured through the revision of the three security documents.