The defence strategic review marks a pivotal shift in Australia’s approach to defence doctrine and strategy, placing a significant emphasis on deterrence. As the government moves to develop a national defence strategy next year, a more nuanced understanding of deterrence is needed. Clarifying Australia’s deterrence-by-denial approach will be vital in turning the DSR’s deterrence vision into practical and effective measures that enhance national security.

Deterrence is the practice of discouraging an adversary from unwanted actions by threatening to increase costs or deny benefits. The DSR calls for a deterrence-through-denial policy—to militarily deny the potential benefits of aggressive action, the most challenging type of deterrence to operationalise with success.

For deterrence by denial to be effective, it must cause an adversary to refrain from taking aggressive action because it believes that it will be militarily denied from achieving the potential benefits. This contrasts with deterrence by punishment, which threatens an adversary with severe penalties, such as conventional strike or sanctions. This strategy relies on imposing costs on an adversary that outweigh the benefits of initiating an action, even if the adversary thinks it could achieve its military goals.

The choice between deterrence by denial and deterrence by punishment has significant implications for force design and structure, operational planning and alliance management.

To maintain credibility in the region and on the world stage, Australia needs to say what it means and mean what it says. What the DSR is saying about deterrence is far from clear.

A deterrence-by-denial approach against an invasion of mainland Australia would likely necessitate an increase in the Australian Defence Force’s capability, beyond what is outlined in the public version of the DSR. For example, it could involve fortifying coastal defences, laying more sea mines, acquiring more anti-ship missiles, and deploying advanced surveillance systems to monitor, detect and deter incursion attempts.

To demonstrate a credible deterrence-by-denial strategy, any time there’s an incursion or testing of defences by an adversary, it must be met with forces that promise denial. But is this the type of strategic approach the DSR is really seeking to achieve? If this deterrence-by-denial strategy has ambitions further afield than deterring mainland incursions, then it presents significant challenges for Australia.

Today’s ADF probably lacks the force structure and posture required to deny most high-level political-military scenarios. Beyond its feasibility, implementing this approach could lead to regional instability if building and demonstrating credible denial capabilities appear threatening to regional neighbours.

It’s important to be candid about the potential unintended consequences of a deterrence-by-denial strategy—but there are a few actions Defence can take now to mitigate risks and strengthen Australia’s deterrence policy and strategy for the future.

First, Defence should reconsider its narrow focus on a singular deterrence-by-denial strategy and explore a more comprehensive and coordinated approach that allows Australia to tap into different deterrence strategies that can be tailored to specific adversaries and situations. Deterrence by denial doesn’t need to be abandoned—and indeed cannot be abandoned given its prominence in the DSR—but it should be seen as just one aspect of a holistic, integrated deterrence approach. Integrated deterrence provides a more flexible framework across services, domains, theatres, the spectrum of conflict, all instruments of national power, and Australia’s network of alliances and partnerships. It would provide a collective toolkit that Australia could use to deter a wider range of potential threats.

Second, a senior government official should be appointed with responsibility for deterrence policy and strategy, along with an appropriate military counterpart, to consolidate Defence’s use of deterrence. A common understanding of Australian deterrence strategy and policy is critical for Defence, the government as a whole and the US alliance. This role must assess who Australia seeks to deter from doing what, how it will do that and in what timeframes. Tabletop exercises, wargaming and red-teaming should be used across the ADF, including intelligence and policy organisations and across domains, to test scenarios to inform capability requirements and decision on force structure and posture.

Third, Australia’s deterrence approach will require proactive escalation management at the whole-of-government level. Defence can start by addressing any misperceptions of Australian capabilities and strategic intentions that could lead to miscalculation. Preparedness activities should involve relevant departments, allies and partners to enhance coordination, communication and decision-making. Effective deterrence requires all the players to efficiently harness the necessary tools of national power for maximum effect. It should also foster communication channels that provide the ability to de-escalate conflict when necessary.

Australia’s security hinges on seeing deterrence not as a one-off strategy, but as a persistent, adaptive process—one that confronts potential threats with a robust, credible and integrated response that makes the cost of aggression untenable.