Buried in the joint statement of an Australia–Japan defence and foreign ministers’ meeting on 6 September was a step-change: Canberra and Tokyo would deepen cooperation on current and future deterrence activities, including flexible deterrent options (FDOs). That moves the partnership up significantly.
At last year’s meeting, the two sides went as far as acknowledging an understanding of each other’s approaches to deterrence. Now we see greater strategic alignment, including planning and moving more closely to deterring together. This is the prerequisite, after which joint FDOs would give both nations a shared ladder of military and non-military options to deliver coordinated and more credible collective deterrence in the Indo-Pacific.
FDOs are preplanned, deterrence-oriented actions used as an operational planning tool. FDOs are developed to facilitate timely decision-making by national leaders through calibrated options designed to signal resolve and influence an actor’s behaviour before or during a crisis. The US Joint Publication 5-0, Joint Planning frames their purpose simply: to send a visible, credible message to shape an opponent’s cost-benefit calculus and to position forces in a manner that, if deterrence fails, facilitates a military response. FDOs raise pressure gradually to avoid unintentional escalation.
While military-centric, FDOs are more effective when coordinated across instruments of national power—diplomatic, informational, military and economic—for combined effect. Practical examples of FDOs include increasing the tempo and visibility of exercises; show-of-force military deployments; threats of sanctions or imposing embargoes; publicising violations of international law; signalling support to allies and partners; and raising public awareness of an international issue and risk. While such options are not novel, what is new is the commitment to plan them with a key partner—by identifying triggers, roles, legal and logistics pathways and coordinated messaging—so they can be activated quickly and coherently, enhancing the credibility of deterrence.
Today, FDOs are a key fixture in the Japanese national security and defence framework and in the Japan-US alliance. They gained prominence in US planning in the 2010s when the Pentagon was identifying ways to harness deterrence for a wider array of unconventional scenarios across the competition continuum that could be tailored to a range of actors and regions for integration with the joint force, inter-organisational partners and allies. FDOs became a critical component of the 2015 Guidelines for Japan-U.S. Defense Cooperation. This created the Alliance Coordination Mechanism for developing and implementing joint FDO responses, as well as synchronise strategic messaging for deterrence and de-escalation scenarios. Since then, the alliance has homed in on roles and missions, improved operational readiness and response capacities and capabilities. To deepen cooperation on posture, capability development and exercises, Japan and the US have sought to leverage their partnership network with other countries that support the rule-based international order.
The 2022 National Security Strategy of Japan and Defence of Japan 2023 reaffirmed Tokyo’s pursuit of a multilayered network with the United States and likeminded countries to strengthen deterrence. Japan does this through dialogue, training and exercising, information-protection agreements, reciprocal access agreements (RAAs), joint development of defence equipment, capacity building support, strategic communication and FDOs. This approach is part of Japan’s deterrence logic of a coordinated deterrence posture: using whole-of-government measures with allies and partners to shape a security environment that is resilient enough to resist attempts at unilateral changes to the status quo by force or coercion.
The latest Australia–Japan joint ministerial statement signals that our special strategic partnership is ambitiously and unambiguously a commitment to collective deterrence in our region, with FDOs as the tool to operationalise strategic alignment. Deterrence succeeds when, by raising the costs or denying the benefits of action, it prevents unwanted behaviour from a potential aggressor dissatisfied with the status quo. For deterrence to be effective, the threat of denial or punishment rests on having the capability to act, credible willingness to carry out the threat, and unambiguous communication of the signal of that threat. Doing that collectively is harder, demanding integration of planning, authorities, messaging and trust.
This partnership is positioned for the task. As Defence Minister Richard Marles said at the joint ministerial press conference, ‘There is no country with whom we have a greater strategic alignment than Japan. We are both democracies. We both support a global rules-based order. We are both allies of the United States [and] there is no country in the world with whom we have greater strategic trust.’ Australia and Japan share common interests and shared a vision, a will and capability to realise a free and open Indo-Pacific, and a stated intent to deter unilateral attempts to change the status quo by force or coercion in the East China Sea and the South China Sea.
The practical enablers are falling into place. The RAA is expediting mutual deployment processes; an acquisition and cross-servicing agreement standardises refuelling, medical, and logistics support; liaison officers are exchanging in operational commands; and force posture cooperation is broadening. Participation by Japan’s Amphibious Rapid Deployment Brigade in US Marine rotations in Darwin is expected to be regularised, as are reciprocal deployments of Japanese and Australian F-35s. The Australian destroyer HMAS Brisbane is heading to the Japan Maritime Self-Defense Force base in Yokosuka. This will be the first instance of Australian resupply and maintenance in Japan in many decades. Such activities greatly enhance interoperability between Australian and Japanese forces and strengthen their projection capabilities.
Both countries are increasing the number, frequency and scale of training and exercises. At the same time, they are bringing each other into their bilateral exercises with partners, laying the groundwork for a network of collective deterrence. Japanese and Australian recent observation of Exercise Salakinib between the Philippine and US armies will be updated to full participation in 2026, enabling Tokyo and Manila the opportunity to exercise their recent signing of an RAA. These examples are some the wide array of defence cooperative activities that point to enhanced interoperability with purpose.
As the 50th anniversary of the Australia–Japan Basic Treaty of Friendship and Cooperation approaches in 2026, both countries are seeking to elevate their defence cooperation as a central pillar of coordination among like-minded partners in realising a free and open Indo-Pacific through collective deterrence. Joint FDOs and the establishment of a standing coordination mechanism are practical next steps. These measures should translate into institutionalisation of bilateral planning with pre-cleared legal and coordination pathways, clear roles and burden-sharing, and calibrated military, diplomatic, informational and economic signalling that can be scaled with partners when required.
This is the partnership to watch as collective deterrence in the Indo-Pacific moves from aspiration to an operational coalition.