Japan’s direct participation in an AUKUS Pillar II initiative marks a significant milestone in regional defence collaboration and underscores the growing importance of underwater autonomous systems in modern military strategy. The recent exercises in Jervis Bay, New South Wales, where Japan joined Australia, the United Kingdom, and the United States in testing underwater autonomous systems (UAS), highlight a strategic alignment that could reshape maritime defence capabilities in the Indo-Pacific.
The exercises, conducted on July 16-17, focused on evaluating the interoperability of UAS through underwater acoustic communication. This marks Japan’s first active participation in an AUKUS exercise, moving beyond its previous role as an observer. The initiative aligns with the broader goals of AUKUS Pillar II, which aims to co-develop and share advanced military technologies beyond nuclear-powered submarines, the focus of Pillar I.
Japan’s involvement was foreshadowed in the September 2024 Joint Leaders Statement to Mark the Third Anniversary of AUKUS, which identified maritime autonomous systems as an initial area of cooperation. The statement emphasised leveraging Japan’s deep technical expertise in this domain, a nod to the country’s longstanding investments in underwater drone technology.
Japan’s Ministry of Defense (MoD) has been actively engaging with domestic firms like IHI, which in 2019 proposed a maritime unmanned/autonomous system featuring an underwater unmanned vessel (UUV) capable of real-time data transmission to unmanned surface vessels (USVs). This system could relay information to support vessels via satellite, demonstrating Japan’s advanced capabilities in autonomous maritime systems.
In mid-2024, IHI secured a ¥37 billion (approx. AU$380 million) tender for Japan’s OZZ-100 underwater automated system (UAV) project. While speculation suggests this system may surpass the depth capabilities of Mitsubishi Heavy Industry’s (MHI) OZZ-5 UUV, the OZZ-5 remains a critical asset. Developed by the MoD’s Technical Research and Development Institute (TRDI), the OZZ-5 is part of a joint research initiative with French defence authorities and Thales S.A. to develop next-generation mine detection technology using synthetic aperture sonar.
The OZZ-5’s compatibility with Japan’s Mogami-class multi-mission stealth frigate adds another layer of strategic significance. This frigate is a contender for Australia’s Sea 3000 General-Purpose Frigate (GPF) program, competing against Germany’s Thyssenkrupp Marine Systems’ (TKMS) MEKO A-200. Japan’s participation in AUKUS Pillar II thus extends beyond technology to potential industrial and defence procurement collaborations.
Japan’s broader defence strategy includes deepening ties with AUKUS nations, particularly Australia. The 2022 Defence Buildup Program (DBP) paper outlined plans to strengthen technological cooperation with AUKUS members and build a close relationship with Australia, second only to Japan’s defence cooperation with the United States. This commitment is reflected in Japan’s 2025 ‘Defence of Japan’ Whitepaper, which positions Australia as Japan’s second-largest partner in international joint research. Current programs encompass hydrodynamic and hydroacoustic performance, automated multiple drone technology, and laser technology applications.
As Japan continues to integrate its defence capabilities with those of AUKUS nations, the recent exercises in Jervis Bay serve as a testament to the evolving nature of regional security alliances. The focus on underwater autonomous systems not only enhances interoperability but also sets the stage for future technological advancements in maritime defence. This collaboration could redefine the strategic landscape of the Indo-Pacific, ensuring that Japan remains at the forefront of defence innovation and regional security.
