Japan and Australia Conduct Trident 25-3 Naval Drill to Uphold Indo-Pacific Maritime Rules.

The Japanese frigate JS Kumano and Australian destroyer HMAS Brisbane conducted the Nichi-Gou Trident 25-3 drill in Sagami Bay, focusing on data sharing and maneuver tactics.

On September 19, 2025, the Japan Maritime Self-Defense Force (JMSDF) and the Royal Australian Navy (RAN) held the Nichi-Gou Trident 25-3 drill, deploying the frigate JS Kumano and destroyer HMAS Brisbane in coordinated maneuvers. The exercise emphasized real-time data sharing and joint tactics, reflecting both nations’ determination to strengthen military interoperability and safeguard Indo-Pacific stability amid rising regional tensions.
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The Japanese and Australian navies are no longer merely symbolic partners, they are increasingly interoperable, combat-ready forces capable of projecting power across the Indo-Pacific (Picture source: Japanese MoD)

The JS Kumano (FFM-2), a Mogami-class stealth frigate commissioned in 2022, represents the new generation of Japanese naval capability, equipped with advanced sensor fusion, a compact hull optimized for littoral and blue-water operations, and a reduced crew requirement through automation. HMAS Brisbane, a Hobart-class air warfare destroyer, brings formidable layered air defense capabilities with the Aegis combat system and SM-2 missiles. Together, these two warships reflect the cutting edge of allied naval engineering, combining speed, precision, and advanced command-and-control to conduct LINKEX, tactical maneuvering, and PHOTOEX drills that replicate real-world maritime operations.

Beyond their symbolic presence, both JS Kumano and HMAS Brisbane are built for high-end maritime warfare and contribute complementary strengths to coalition operations. JS Kumano is armed with a 127mm naval gun, Mk 41 Vertical Launching System (VLS) cells capable of deploying surface-to-air and anti-submarine missiles, and a SH-60K helicopter for extended anti-submarine and surveillance missions. Its stealth features and compact multi-mission design enable it to operate effectively in contested littoral zones while still maintaining blue-water endurance. HMAS Brisbane, on the other hand, is designed as a fleet air-defense backbone, integrating the Aegis Baseline 9 system, SPY-1D(V) radar, and vertical launch cells configured for Standard Missiles and Evolved Sea Sparrow Missiles (ESSM), giving it the ability to defend against saturation missile attacks and airborne threats across vast maritime domains. Together, these ships represent a potent force multiplier, capable of executing integrated air defense, anti-submarine warfare, and surface strike missions with high precision and survivability in multi-domain operations.

Joint exercises like Nichi-Gou Trident 25-3 go beyond technical interoperability, they shape the regional security environment by enhancing mutual trust, sharpening warfighting synergy, and preparing both navies for integrated operations in crisis scenarios. The ability to conduct seamless communications via LINKEX and execute coordinated maneuvers signals a level of operational cohesion essential for coalition warfare. These activities also act as strategic messaging to adversarial powers that any attempt to destabilize regional maritime security will be met with unified, ready, and technologically advanced naval forces.

The geostrategic implications of this drill are profound. As China continues to expand its naval presence and conduct aggressive maneuvers across the South and East China Seas, Tokyo and Canberra are intensifying efforts to anchor a coalition of like-minded democracies with credible maritime power projection. By forging a robust bilateral military architecture, Japan and Australia are creating strategic depth beyond U.S. force posture, building an autonomous layer of deterrence. This trilateral alignment with Washington is reshaping Indo-Pacific deterrence from a hub-and-spoke model into a more networked and distributed defense framework capable of responding to multi-theater contingencies.

The Japanese and Australian navies are no longer merely symbolic partners, they are increasingly interoperable, combat-ready forces capable of projecting power across the Indo-Pacific. As both countries modernize their fleets and tighten bilateral defense ties, their combined naval drills serve as an unmistakable strategic posture to uphold a Free and Open Indo-Pacific, challenging authoritarian encroachment and fortifying a new lattice of maritime security in Asia’s most volatile waters.

Written by Teoman S. Nicanci – Defense Analyst, Army Recognition Group

Teoman S. Nicanci holds degrees in Political Science, Comparative and International Politics, and International Relations and Diplomacy from leading Belgian universities, with research focused on Russian strategic behavior, defense technology, and modern warfare. He is a defense analyst at Army Recognition, specializing in the global defense industry, military armament, and emerging defense technologies.