Two Challenges Posed by the Naval Build-Up of Japan and South Korea to the Chinese Navy in 2026

On September 15, Breaking Defense reported that as the Chinese Navy significantly outpaces Pacific nations in terms of the number of vessels, total tonnage, and operational capabilities, Japan and South Korea are hastening the reconstruction of their naval forces. From the perspective of the author, who has observed the operations of the escort fleet in Yokosuka, this does not appear to be a simple "competition of vessel numbers." The focus is on how long they can protect maritime trade routes with limited personnel and budgets.

The Reality of Mass Production Shown by Japan's Mogami Class

The Japan Maritime Self-Defense Force is attempting to integrate anti-submarine warfare, mine warfare, and patrol capabilities centered around the crew-efficient Mogami-class frigates. With a standard displacement of approximately 3,900 tons and a length of about 133 meters, the design emphasizes labor-saving compared to traditional multi-role escort vessels. Australia's choice of the improved Mogami class indicates that not only the vessels themselves but also Japan's design, maintenance, and training systems are approaching a form that can be exported.

South Korea Complements with Submarines and Large Surface Ships

The South Korean Navy is expanding its options by combining KSS-III class submarines with large air defense ships, enabling operations not only around the Korean Peninsula but also in more distant waters. While Japan's strength lies in quiet anti-submarine patrols and supply networks, South Korea's concept is to enhance vertical firepower, including ballistic missile defense and long-range strikes. Both countries see the same threats, but their combinations of capabilities and intentions are not identical.

Implications for the Japan-U.S. Alliance

Japan's 2026 Defense White Paper positions China as the "greatest strategic challenge" and outlines plans to establish SHIELD (Synchronizing and Integrating Coastal Defense) by fiscal year 2027, including unmanned systems. The key point here is not for Japan and South Korea to become substitutes for the U.S. Navy. Japan will take responsibility for the southwestern islands and SLOCs (Sea Lines of Communication), while South Korea will handle anti-submarine and air defense around the peninsula and in Northeast Asia, allowing U.S. forces to concentrate expensive major vessels in critical maritime areas through this division of labor.

The true constraints lie not in the shortage of hulls but in personnel, munitions, maintenance bases, and the political processes for rapidly sharing classified information among the three countries.

Overlooked Vulnerabilities

However, fleet modernization does not immediately equate to enhanced combat power. Even with an increase in new vessels, if there is a shortage of training fuel, spare parts, and aircraft and sonobuoys to support anti-submarine warfare, operational rates will not improve. Historical awareness and export controls remain points of friction in Japan-South Korea cooperation. Therefore, what will determine the deterrent effect on the Chinese Navy is not the announcement of the number of commissioned vessels, but whether both countries can operate with the same maritime charts and information during the first 72 hours of a crisis.

Key Sources: Breaking Defense (September 15, 2026), Defense News (Japan 2026 Defense White Paper), Ministry of Defense of Japan / Self-Defense Forces.