In this fortnightly online column, ADM journalist Corey Lee Bell covers defence news across Japan and the Republic of Korea.
Japan kicks off participation in AUKUS Pillar II with underwater drone tests
Japan directly participated in an AUKUS Pillar 2 initiative for the first time during this year’s Exercise Talisman Sabre, Australia’s largest multilateral military exercise.
Pillar 2 refers to the pact between AUKUS partners Australia, the United Kingdom and the United States to co-develop and share military technology beyond the purview of nuclear-powered submarines, which is the domain of the AUKUS Pillar 1 agreement.
According to a statement issued by Japan’s Ministry of Defense, on July 16-17, Japan and the three AUKUS partners jointly conducted experimental exercises in Jervis Bay, New South Wales, which involved communicating with underwater autonomous systems (UAS) via underwater acoustic signals, and “evaluated the[se systems’] interoperability.”
The tests, which are part of the AUKUS partners’ “Maritime Big Play” integrated experiment series, marked the first occasion in which Japan has joined an AUKUS exercise as an active participant as opposed to an observer.
Plans for Japan to cooperate with the three AUKUS partners were first flagged in September 2024’s ‘Joint Leaders Statement to Mark the Third Anniversary of AUKUS.’
The announcement came several months after the AUKUS nations’ Defence ministers jointly “announced principles for additional AUKUS Pillar II partner engagement on specific projects where new partners could contribute to, and benefit from, AUKUS.”
The September statement’s focus on “maritime autonomous systems” as an “initial area of cooperation” with Japan was also linked with the aim of “leveraging Japan’s deep technical expertise” in that area.
In 2019, Japanese press reported that domestic firm IHI had approached Japan’s Ministry of Defense (MoD) to promote a “maritime unmanned/autonomous system” which included an underwater unmanned vessel (UUV) capable of sending sonar imagery to an unmanned surface vessel (USV), the latter of which could pass on communications with support vessels in real time via satellite linkage.
In mid-2024, IHI was awarded a ¥37 billion-yen (approx. AU$380 million) tender for Japan’s OZZ-100 underwater automated system (UAV) project.
There has been conjecture among Japanese military bloggers that this system will feature sea mine detection capabilities at greater depths than Mitsubishi Heavy Industry’s (MHI) OZZ-5 UUV.
However, the OZZ-5, developed by the MoD’s Technical Research and Development Institute (TRDI), also currently features in a joint research arrangement with French defence authorities and Thales S.A. aimed at developing “next generation mine detection technology” utilising a combination of low and high frequency synthetic aperture sonar technology.
The OZZ-5, furthermore, is expected to be capable of being loaded on the Mogami-class multi-mission stealth frigate, which is competing against Germany’s Thyssenkrupp Marine Systems’ (TKMS) MEKO A-200 for a contract under Australia’s Sea 3000 General-Purpose Frigate (GPF) program.
Japan’s participation in an AUKUS Pillar 2 initiative also comes against the backdrop of broader efforts by Tokyo to deepen defence tech and industries ties with the three AUKUS nations, in particular, Australia.
Japan’s 2022 Defence Buildup Program (DBP) paper announced plans to “strongly promote technological cooperation” with each of the AUKUS nations, and “build the closest cooperative relationship [with Australia] second only to the Japan-US defence cooperation and deepen [bilateral] consultations in all levels including… defence equipment and technological cooperation.”
Australia features prominently in Japan’s MoD’s 536 page 2025 ‘Defence of Japan’ Whitepaper (Japanese version), where it is presented as already being Japan’s second largest partner in “international joint research” in terms of the volume of current programs, which include cooperation via scientific and technical exchange, as well as joint research on hydrodynamic and hydroacoustic performance, automated multiple drone technology, and laser technology applications.