What would Australia be willing to go to war over? This needs to be made clear in our defence strategy

In 2024, the National Defence Strategy made deterrence Australia’s “primary strategic defence objective”.

With writing now underway for the 2026 National Defence Strategy, can Australia actually deter threats to the nation?

Traditionally, our defence strategy only asked that our military capabilities “command respect”. In today’s world, however, Australia needs a far more active military posture to defend itself.

To effectively deter an adversary, Australia needs the equipment, signals and processes to convince a potentially hostile nation to reconsider the cost of militarily threatening us.

A deterrence strategy promises to reduce the likelihood of conflict. It reduces the opportunities for an adversary to score “cheap” wins by communicating how we could “deny” their main goal and potentially “punish” them for their aggression.

It forces an adversary to make a choice: back down or risk failing at your objective and starting a more significant confrontation.

While we don’t know exactly how a future adversary might react, Australia must do more to make our intent clear on how we would respond to a provocation.

We are part of an international team researching the ways to do this. This is what we think is needed in the next National Defence Strategy.

What deterrence looks like

Creating a credible deterrence posture is not easy. The 2024 defence strategy lists a wide variety of actions that could change an adversary’s risk assessment.

Some of these things are specific (surveilling and protecting Australia’s sea lanes of communication). Others are vague and loosely connected to deterrence (supporting the global rules-based order).

To make sure our deterrence message is as clear and effective as possible, the 2026 strategy will need a much tighter policy framework around where Australia would have the power to deter an adversary, and how we would do so.

It will also need to detail the specific defence preparations Australia has undertaken to credibly deter threats.

Vagueness in language or generalities in proposed actions will not cut it.

What history can teach us

The scholarly literature on how to implement an effective deterrence is largely drawn from Cold War history.

Many times, the US and USSR made deliberate efforts to send deterrence signals to the other side. They did this by acquiring new capabilities (such as longer-range missiles) and expanding their nuclear stockpiles, or by conducting military exercises and deploying forces around the world. These messages, however, were often misunderstood.

Sometimes, these signals – such as US President John F. Kennedy’s reinforcement of West Berlin with an additional battalion during the Berlin Crisis of 1961 – made political sense, but less so militarily.

One way for Australia to approach this deterrence question is considering the adversary’s theory of victory – how they seek to achieve their goal – and then identifying ways to explicitly and publicly show we can disrupt it.

For example, after winning the 1982 Falkland Islands War against Argentina, Britain invested significant resources into the Mount Pleasant Air Base on the islands. They are now home to up to 2,000 personnel, enabling significant and rapid reinforcements in the event of future hostilities.

The use of ‘trip wires’

Australia is now acquiring significant new strike capabilities. However, even if we increase our defence spending beyond the 3% of GDP currently being discussed, the Australian Defence Force (ADF) will not be able to defend everything across the entire region and the waters around us.

We will need to find low-cost defensive actions.

Deterring an adversary from attempting a “cheap win” against Australia, for instance, might require the “forward presence” of Australian troops far from our own shores. Even if they would not be able to defend against an attack on their own, they could serve as a “trip wire” force. This means if they were attacked, it would likely compel Australia to go to war.

So, let’s say Australia has a “forward presence” of troops stationed in the Cocos Islands, Papua New Guinea or even the Philippines. This signals a credible commitment to use those forces to protect ourselves and our regional partners against a threat. And should these soldiers be killed, it would likely generate public anger and a political insistence on a significant response.

While a lot of contemporary military thinking is about how to put robots and drones in harm’s way instead of our fellow citizens, some tasks, such as a “forward presence” deterrence, can likely only be done by humans.

We need to be clear about red lines

All of this means that deterrence is not just about a country’s capabilities – going to war is ultimately about politics, and human emotion.

As such, credibility also depends on practical rituals – such as Britain holding Cabinet meetings in the Falklands and NATO hosting flag parades in the Baltics. These convey a belief over what matters enough to go to war.

For Australian deterrence to be more credible, the next iteration of the National Defence Strategy will have to be more explicit than its predecessor in spelling out what Australia would be willing to go to war over.

If our government cannot address this now, how are we going to communicate this to an adversary – and convince them of it – in a crisis?

The government is understandably reluctant to be specific about the commitments and threats it is willing and able to make in a public document, or to acknowledge the limits to Australia’s abilities.

But deterring without communicating is a contradiction in terms. We need to be explicit about what would cause Australia to resist or retaliate, even at the cost of war, in order to credibly deter an adversary from taking such an action.This must be at the core of how the 2026 National Defence Strategy approaches deterrence as Australia’s “primary defence objective”.

This piece is part of a series on the future of defence in Australia. Read the other stories here.