A geographic reality for Australia is that almost all physical threats to its sovereignty will first need to compromise the sovereignty of one or more of its northern neighbours. It is perhaps for that reason that the defence strategic review ^[1] once again affirms Australia’s commitment to the security of its allies and partners in the region and the global rules-based order.

But how should the Australian Defence Force respond if a threat to a neighbour’s sovereignty might lead to Australia or its interests being threatened? The response, a ‘Plan B ^[2]’, should be for Australia to aim to deter aggression in the first place by adding ‘support to resistance’ to its portfolio of strategic options.

Resistance ^[3] in this context is ‘a nation’s organised, whole-of-society effort, encompassing the full range of activities from nonviolent to violent, led by a legally established government (potentially exiled/displaced or shadow) to re-establish independence and autonomy within its sovereign territory that has been wholly or partially occupied by a foreign power’.

In other words, resistance may be nonviolent, as with the Danish resistance to German occupation in World War II; an insurgency, as in the Afghan mujahideen resistance to the Soviets in the 1980s; or a hybrid response, as has been typical of Ukrainian tactics following Russia’s full-scale invasion in February 2022.

In an article for the Australian Journal of Defence and Strategic Studies ^[4], I explain what a resistance strategy is, the recent history of developing and employing such strategies in Europe, and why this matters to Australia in the context of major-power competition today. I also point to subtle efforts from the US, UK and NATO to support Ukraine’s development of an effective resistance strategy.

The notion that a resistance strategy might deter by denial was tested in World War II when the Wehrmacht prepared a plan to invade Switzerland ^[5]. Following the fall of Denmark, Norway, the Low Countries and France in 1940, the German calculus was that 21 divisions would be required for an invasion of Switzerland. The objective was to open alpine transport links to Italy, but the tunnels and bridges on those links were prewired by the Swiss for demolition. The potential denial of the very aims of an invasion, and the opportunity costs it entailed, were thus more than Hitler could bear. The Nazis, commenting on the Swiss barbed-wire fortifications along its borders, began to describe the Swiss system of defence as a ‘porcupine’, and thus the ‘indigestible hedgehog’ metaphor of resistance strategy was born.

If the aggressor is undeterred, a resistance strategy that relies on insurgency is still useful. Insurgencies impose costs—in materiel, personnel, reputation, money and ethics or morality—but to be most effective, they must be prepared prior to hostilities with an appropriate focus on control over the legal, moral and ethical employment of force.

The ADF and Australian policymakers—and indeed Western nations more broadly—have an acute understanding of the costs that might be imposed by an insurgency. Australia experienced such costs during its military commitments to counter insurgencies in the Middle East over the past two decades. Contrary to some recent commentary, organisational learning about insurgencies through these commitments may not have been a ‘distraction’ from contemporary defence challenges after all. Importantly, the West also lost to an insurgency in Afghanistan, despite having overwhelming technological, numerical and doctrinal advantages.

A profound irony in Australian military culture is thus highlighted by the defence strategic review. Despite a stated objective to create ‘asymmetry’ and ‘deter by denial’, the review shows how quickly we have forgotten that insurgents created asymmetries against us and denied the West victory.

The implication when considering a pacing threat that has greater mass, greater range and greater technological advantages ^[6] is simple. An asymmetric strategic option for the ADF is to support the resistance efforts of our neighbours against an aggressor that might occupy some or all of their territory. This strategic option, if communicated effectively to would-be aggressors, might deter by denying them the quick fait accompli seizure they desire of a targeted region or country. An aggressor would know that a resistance movement will have been established that is capable of waging a prolonged insurgency; that the armed forces of a targeted country will receive training and materiel assistance to sustain the fight for their homeland; and that targeted political leadership will be helped to maintain a government-in-exile that denies a quisling government legitimacy internationally and domestically. If all of this is communicated effectively, the aggressor will know that the invaded country will receive support from Australia to fight back and endure.

A commitment to support the resistance efforts of targeted countries thus reinforces the global rules-based order by dissuading acts of military aggression. And Australia can then benefit from strategic depth in defence.

Resistance strategy is, notably, reliant on resilience. A targeted country must be able to absorb the disruption caused by a military invasion. Many of the considerations in developing resilience to military action are similar to what a society requires to be resilient to disruptive climate events, terrorism or pandemics. Support to a resistance strategy thus develops capacity and capabilities that might reduce the requirement for ADF contingency operations. Indeed, attention to developing resilience with our partners might also help to enhance Australian resilience.

A strategy of support to resistance is asymmetric in that doesn’t depend on a ‘qualitative edge’ or a major research investment. Instead, it depends on people—their selection, training, management and education—and an effective concept of their employment. It is also asymmetric in that it enhances the likelihood of successful conventional military operations by dispersing threat forces, thus denying them the ability to concentrate. This dilemma was exemplified by the Allied support to the French resistance in World War II and the orchestrated maquis uprisings that occurred immediately prior to the Normandy landings. Doctrine explaining such requirements that might support policymaking, education and training is absent in the Australian context. It is therefore a ‘Plan B’ by being able to augment the conventional military power that our ‘Plan A’—the defence strategic review—articulates.

A final irony is, of course, that the West has already unconsciously adopted such a strategy through its military support to Ukraine. We have stood up and stated that we will not abide the aggressive actions of nations that erode the rules-based order. The only question is whether we could have done so more effectively or efficiently.

A commitment to a strategy of deterrence by denial should look to the recent efforts by Eastern Europe to deter Russian aggression and the support to such resistance strategies that have been conducted by NATO. It should look to the lessons from resistance concepts employed in Ukraine and develop appropriate doctrinal models for how a resistance strategy might be supported in the future.

An Australian strategy of support to regional resistance can learn from this recent operational experience to deter autocratic regimes in the Indo-Pacific.