The Burden of Simultaneous Deployment in Two Maritime Areas as Indicated by JMSDF's Participation in RIMPAC 2026 and Sea Breeze

On July 13, a line was added to the Japan Maritime Self-Defense Force (JMSDF) press release stating, "Regarding participation in the U.S.-Ukraine co-hosted multinational exercise (Sea Breeze 2026)." On the same day, there was a Japan-Tonga joint training, and three days prior, a Japan-NATO joint training, in addition to JMSDF's participation in the U.S. Navy-hosted multinational joint exercise RIMPAC 2026. This is not a flashy announcement of new weapons. However, the lineup of these training schedules well illustrates the breadth of missions currently faced by the JMSDF.

Concentration of Training Events in Mid-July

According to JMSDF's public materials, participation in Sea Breeze 2026, the Japan-Tonga joint training, the Japan-NATO joint training on July 10, and the Japan-U.S. joint training on July 8 are listed. RIMPAC has been held almost biannually since 1971, and 2026 will mark the 30th iteration, with JMSDF's participation being the 24th since 1980. In other words, involvement in large-scale multinational exercises in the Pacific and the U.S.-Ukraine co-hosted exercises focused on Europe and the Black Sea are overlapping in the same month.

What I find noteworthy is not the mere participation itself, but the geography of the training. RIMPAC, held around Hawaii, is a familiar stage for the JMSDF, but Sea Breeze has become an exercise linked to practical lessons learned regarding maritime routes, mines, coastal defense, and unmanned systems in the context of the Russia-Ukraine war. Even if these areas are distant from Japan, the tactical knowledge accumulated there is not unrelated to the defense of the Nansei Islands.

JMSDF Must Learn Beyond Just the Russia Conflict

What has become clear in the Black Sea is the reality that large surface ships are exposed to a complex threat from coastal missiles, unmanned surface vessels, unmanned aerial vehicles, and mines. In the waters surrounding Japan, the Chinese Navy and Coast Guard, the Russian Pacific Fleet, and North Korea's missile capabilities all coexist simultaneously. If we separate capabilities from intentions, not everything is immediately directed at Japan. However, it is undeniable that the opposing side is increasing its complex maritime denial capabilities.

Involvement in Sea Breeze holds more value in the less glamorous areas of mine sweeping, port protection, maritime transport security, and unmanned vehicle countermeasures than in the flashy formations of escort ships. During the Cold War, the JMSDF's central task was to protect SLOCs (Sea Lines of Communication) from Soviet submarines. In 2026, the JMSDF must rethink the same SLOC defense in an environment where missiles and unmanned vehicles are mixed.

Advantages of RIMPAC and Personnel Constraints

RIMPAC 2026 serves not only as a venue for cooperation among Japan, the U.S., Australia, and Canada but also as a testing ground for logistics, communications, at-sea repairs, and joint target identification. The lessons learned from the exercise will vary depending on which escort ships, P-1 patrol aircraft, submarines, or mine warfare units are dispatched. The most significant aspect for the JMSDF is the ability to connect its forces to the U.S. Navy's theater-level command and control, allowing them to measure the difference in speed between receiving information and making their own judgments.

However, there is a structural problem here. As long-distance training increases, there will be a strain on domestic vigilance and monitoring, readiness in the Nansei Islands, maintenance and repair, and personnel training. In 2026, while the JMSDF is advancing the reorganization of its surface fleet, it continues to face issues with securing personnel. While the number of training events is a strength in terms of alliance operations, it is also important to remember that the organizational capacity to absorb training is not infinite.

Japan's Role Is Not Limited to Blue Water Deployment

Participation in Japan-NATO joint training and Sea Breeze demonstrates Japan's intention to link European security with the Indo-Pacific. This is diplomatically effective, as it prevents the European side from viewing issues in the Taiwan Strait and the East China Sea as merely "regionally limited crises."

However, the military benefits lie elsewhere. What Japan should learn from European navies includes operational techniques for rotating a small number of vessels over extended periods, port protection, integration with civilian shipping, and the political costs of mine warfare. Particularly, mine warfare tends to be sidelined in discussions about the defense of the Nansei Islands, but if supply ships cannot enter ports, no matter how many long-range missiles are deployed, combat sustainability will diminish.

The effectiveness of training should be measured not by the number of participating countries but by how much it can change the distribution of tasks within Japan.

This series of announcements indicates that the JMSDF is attempting to learn not only from the Pacific but also from European-style maritime warfare. However, in my view, the true weakness is not the low participation in exercises. It is the speed at which lessons learned in distant seas are integrated into the daily maintenance and personnel assignments in Sasebo, Yokosuka, Kure, and Maizuru. If this is slow, simultaneous deployment in two maritime areas will become not a strategic intention but merely a crowded schedule.