Tokyo and Canberra Orchestrate Efforts to Multilateralize the South China Sea

This past June, Japan and Australia conducted bilateral military exercises in the South China Sea. Amidst China’s growing military assertiveness in the region, the exercise demonstrated the two countries’ increasing cooperation on maritime security. As the waterway supports over 40% of Japan’s trade and almost 90% of Australia’s fuel imports, stability in the South China Sea is vital for the economic and security interests of these non-claimant states.

Recent remarks from Australia’s new Ambassador to Japan well-encapsulate the motives behind their increased collaboration: both countries seek to preserve stability, freedom of navigation, and freedom of overflight in the South China Sea while maintaining stable bilateral ties with Beijing. This strategic alignment, centered on an inclusive rules-based maritime order, has also enabled both countries to pursue wider regional partnerships centered on achieving stability in the South China Sea.

Growing Cooperative Efforts

Trilateral action between Japan, Australia, and the United States on the South China Sea dates back over a decade. In July 2011, the three conducted their first joint maritime military exercise in the South China Sea. Flare-ups in the sea have since taken on greater importance within the discourse of the Trilateral Security Dialogue: their 2022 press release expressed concern that China’s activities in the region “gravely affect international peace and stability.”

These trilateral efforts created the foundation for emboldened bilateral cooperation between Japan and Australia, which has made significant strides in the past year. Last June, the Australian Parliament published a brief on Australia-Japan relations, noting that responses to China’s “grey-zone activities in both the East China Sea region and the South China Sea” would be a potential area for greater military cooperation. Since then, the two updated their Joint Declaration on Security Cooperation: its 2022 iteration focuses extensively on affirming their commitment to maintaining a “stable and secure maritime domain.” The June 2023 bilateral “Trident” exercise in the South China Sea demonstrates this effort.

Strategic Convergence

On the regional stage, Japan and Australia have rallied behind the vision of a “Free and Open Indo-Pacific” (FOIP). The FOIP stresses the importance of territorial dispute resolution under international law, particularly the 1982 United Nations Convention on the Law of the Sea and the 2016 arbitral ruling on the South China Sea. More significantly, it aims to maintain the rules-based order and uphold freedom of navigation and overflight over the area. The FOIP’s philosophy that no country is excluded from this vision—so long as it abides by a rules-based order—reflects Japan and Australia’s desire to balance the conflicting interests of regional players.

Namely, both states have been careful not to alienate China in their approach. Their economic relations with China are such that retaliatory measures from China would be detrimental to trade in their respective countries. To avoid antagonizing China, the National Security Strategy of Japan characterizes China as a “a matter of serious concern” rather than explicitly a “threat.” Australia’s Defence Strategic Review similarly avoids labelling China as a military threat, noting instead that China’s actions “[threaten] the global rules-based order in the Indo-Pacific in a way that adversely impacts Australia.” The Australian Labor government's attempts to stabilize relations with Beijing match existing hopes among the Australian public for stable ties with China.

Japan, a close neighbor of China, is particularly careful not to act in ways deemed “provocative.” In August 2018, China lodged a protest after two Japanese Maritime Self-Defense Force planes flew near China-occupied Mischief Reef in the Spratly Islands. The move raised concerns about the future of tensions between China and Japan in the East China Sea. Now within China’s missile range, Australia is also growing wary of any action that could escalate tensions.

Furthermore, the two countries also seek to balance the wide range of priorities within ASEAN, where both claimants and non-claimants rely heavily on economic ties with China. With ASEAN states concerned over being drawn into U.S.-China competition in the region, Japan and Australia have sought to dilute that dynamic of South China Sea tensions in favor of promoting free navigation and overflight for all. While Australian collaboration with ASEAN has historically been limited (with greater emphasis placed on the Pacific Islands), it joins Japan in supporting ASEAN centrality and unity on the topic.

Multilateralizing the South China Sea: Progress and Prospects

With the need to maintain stable ties with several regional actors, Japan and Australia have sought to multilateralize discussions on the South China Sea. The two have turned to ASEAN-led multilateral forums such as the ASEAN Regional Forum and the East Asia Summit to voice concerns over China’s increased military assertiveness in the South China Sea and call on participants to commit to securing freedom of navigation based on the rule of law.

Further, Japan has expanded efforts to increase multinational engagements. In 2012, the Expanded ASEAN Maritime Forum was established based on Japan’s proposal, and is now a major forum for discussing regional maritime issues. Japan has also sought to enhance the maritime law-enforcement capabilities of ASEAN states through multiple training and capacity-building programs. Australia could potentially act in concert with Japan on this front, based on its current “Plan of Action to Implement the ASEAN-Australia Strategic Partnership.”

Japan and Australia have also been enhancing cooperation with other regional partners.  The Quad has been a key outlet for Japan, Australia, India, and the United States to discuss maritime issues, and has largely focused on the FOIP vision since it re-formed in 2017. Japan participated in the first-ever trilateral coast guard exercise in the South China Sea with the Philippines and the United States this past June, with Australia participating as an observer. Australia has ample room to boost its own security ties with the Philippines— the formalization of an annual strategic defense dialogue and the first-ever Japan-Australia-U.S.-Philippines defense ministerial talks are both indicators that steps are being taken towards such a partnership.


In recent years, Japan and Australia have been converging in their priorities for the South China Sea, uniting under a vision of a FOIP. The two states are aiming for an inclusive, maritime rules-based order that does not exclude any regional players. To gather support from regional actors, Tokyo and Canberra can be expected to continue aligning their multilateral efforts to maintain peace and stability in the Indo-Pacific region.

Reika Herman was a research intern with the Japan Chair at the Center for Strategic and International Studies.

Mai Takahata is a research intern with the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies.

Reika Herman

Research Intern, Japan Chair

Mai Takahata

Research Intern, Asia Maritime Transparency Initiative