There is a comforting fiction at the heart of much contemporary strategic thinking: conventional military capabilities can substitute for nuclear deterrence without requiring the same political will. It is a neat idea—reassuring, technologically optimistic, and politically convenient. It is also dangerously wrong.

Deterrence does not reside in platforms, precision, or posture. It resides in belief—specifically, the adversary’s belief that you are both capable of inflicting costs and willing to do so. Strip away that second element, and deterrence collapses into theater.

This is the central problem confronting Australia and its allies as they navigate a rapidly shifting Indo-Pacific security environment. As nuclear risks grow, particularly with China’s expanding arsenal, there has been a noticeable intellectual pivot toward elevating conventional capabilities as a more “usable,” credible, and politically palatable form of deterrence. Long-range strike, autonomous systems, undersea warfare, and advanced ISR are all presented as tools that can impose meaningful costs without crossing the nuclear threshold.

However, this argument only holds if those tools are used. Too often, the debate stops at capability acquisition. Billions are spent, platforms are announced, doctrines are drafted. Yet, there is a conspicuous silence when it comes to the harder question: under what circumstances would Australia employ these capabilities in anger? What thresholds trigger their use? What risks are we prepared to accept in doing so?

Without clear answers, the signal sent to adversaries is not strength, but hesitation. Consider the logic from the perspective of a competitor. If Australia invests heavily in long-range strike but avoids articulating when it would employ it, an adversary may conclude that those capabilities are politically constrained. If grey-zone coercion, such as the deployment of sea mines, harassment of maritime assets, or interference with undersea infrastructure, does not elicit a forceful response, then the lesson learned is not deterrence, but permissiveness.

In this sense, ambiguity is not always stabilizing. It can just as easily invite probing. The uncomfortable reality is that conventional deterrence demands a level of resolve that many policymakers are reluctant to acknowledge. Unlike nuclear weapons, whose very horror lends them a paradoxical clarity, conventional forces sit in a murkier space. They are more usable, but precisely for that reason, credibility hinges on demonstrated willingness.

A missile that will is restricted from use is not a deterrent. A submarine that will not be deployed into contested waters does not shape adversary behavior. A cyber capability that remains permanently in reserve does not impose costs. Deterrence, in the conventional domain, is performative. It must be signaled, exercised, and at times demonstrated.

This does not mean recklessness or a rush to escalation. It means recognizing that deterrence is not cost-free. If the objective is to prevent adversary action, then one must be prepared to act before the situation becomes intolerable. Waiting until costs are imposed on you, economically, militarily, or politically undermines the very logic of deterrence. This is where much of the current discourse falls short. There is a tendency to treat conventional capabilities as inherently stabilizing, as though their mere existence alters adversary calculations. But capabilities without credible intent are inert. Worse, they can create a false sense of security, masking the erosion of deterrence beneath a veneer of preparedness.

The challenge is particularly acute for middle powers like Australia, which rely heavily on alliances and extended deterrence. As questions grow around the credibility of U.S. nuclear guarantees, especially in a more contested and multipolar environment, there is an understandable desire to bolster national self-reliance through conventional means. This is a sensible objective. But it cannot be achieved through hardware alone.

If conventional forces are to serve as a substitute or even a supplement to nuclear deterrence, then they must be embedded within a clear framework of political resolve. This requires more than capability development. It requires declaratory policy, strategic signaling, and a willingness to accept escalation risks.

For example, if the laying of sea mines in Australian waters is deemed unacceptable, then that must be stated clearly and backed by a credible commitment to respond with force if necessary. Anything less invites incremental encroachment. Over time, such encroachment normalizes behaviors that would once have been considered intolerable.

History offers ample evidence of this dynamic. Deterrence erodes not in dramatic moments, but through a series of small, unchallenged actions that cumulatively shift the baseline of what is acceptable. By the time a clear red line is crossed, it is often too late as the adversary has already recalibrated expectations.

The solution is not to abandon conventional deterrence, but to take it seriously. This means confronting uncomfortable questions. Are we prepared to use long-range strike capabilities against an adversary’s military assets in the initial stages of a crisis? Would we target grey-zone actors operating below the threshold of armed conflict? How do we signal our intentions without triggering the very escalation we seek to avoid? There are no easy answers, but avoiding the questions altogether is not a strategy, it is an abdication.

Ultimately, deterrence is about shaping perceptions. It is about convincing an adversary that the costs of action will outweigh the benefits. This cannot be achieved through ambiguity alone, nor through capability acquisition in isolation. It requires a coherent integration of means, messaging, and above all else, will.

If policymakers are unwilling to countenance the use of conventional force, then they should be honest about the implications. In such a scenario, conventional capabilities do not replace nuclear deterrence; they merely decorate its absence.

The risk is not just strategic failure, but strategic surprise. An adversary that perceives a gap between capability and intent will exploit it; once that perception is formed, it is exceedingly difficult to reverse.

Deterrence, in the end, is a test of credibility and resolve. It is not measured by what you possess, but by what an adversary believes you will do. In strategic competition, credibility is not claimed; it is proven and without resolve, deterrence is nothing at all.

Natalie Treloar is the Australian Company Director of Alpha-India Consultancy, a Senior Fellow at the Indo-Pacific Studies Center (IPSC), a Senior Analyst at the National Institute for Deterrence Studies (NIDS), and a member of the Open Nuclear Network. Views expressed in this article are the author’s own.

Deterrence Without Resolve Is No Deterrence at All was originally published on Global Security Review.

The escalating tensions with Iran present a serious problem that cannot be ignored. The continued attacks on American troops by Iranian proxies underscores the urgent need for the Biden administration to define and communicate clear red lines to prevent further acts of aggression and protect the lives of American military personnel in the region.

 The Need for Red Lines

 Firstly, the absence of a defined red lines allows Iran to push the boundaries of acceptable behavior without facing substantial consequences. Currently the Biden administration is “weighing responses” to the attack. However, red lines were required once the administration entered office. Iran needed a clear picture of aggression’s consequences, especially aggression causing American casualties. This continued lack of clarity from the administration not only undermines the safety of American soldiers but also weakens the credibility of the United States on the international stage. Without a clear stance, there is a risk of further attacks and a wider regional conflict.

Secondly, defined red lines serve as a deterrent, signaling to Iran that the United States will not tolerate attacks on its military personnel. Establishing such boundaries is essential to maintaining stability in the region and preventing an escalation that can have far-reaching consequences. This sends a powerful message that acts of violence will not go unanswered, fostering a more secure and predictable relationship.

Furthermore, the ambiguity surrounding American responses can embolden other hostile actors in the region and elsewhere to test the waters. Clear red lines are not only about dealing with Iran but also about deterring other potential aggressors and ensuring that the United States is perceived as steadfast and resolute in defending its interests. The Biden administration must follow through on any violations of red lines to solidify credibility.

 The American Response

 To address this critical issue, the Biden administration must take decisive action. First, it is imperative to communicate clear and non-negotiable red lines to Iran, making it unequivocally clear that attacks on American soldiers will trigger severe consequences. Simultaneously, diplomatic engagement with Iran is needed to convey the seriousness of the American position, emphasizing the importance of de-escalation and constructive dialogue—but always backed by the threat of overwhelming violence.

However, to fortify its position and respond effectively to the heightened tensions with Iran, the United States must go beyond diplomatic initiatives and reinforce its military capabilities in the region. The US should bolster its military presence, which serves as both a deterrent and a tangible demonstration of the nation’s commitment to protecting its interests and ensuring the safety of its troops and allies. A visible and formidable American military presence sends a powerful signal, not only to Iran but to the entire region. The United States is prepared to defend its interests and respond decisively to any acts of aggression.

Additionally, the US must respond forcibly to the recent attack. As William Wechsler recently argued, it should be done in ways to avoid a wider regional war from occurring. Matthew Kroenig, however, suggests the United States can incapacitate the Iranian navy. It could conduct strikes on Iranian naval bases or even emulate former President Donald Trump’s approach by targeting Iranian leadership, as demonstrated in the killing of General Qassem Soleimani in Iraq. Additionally, the Biden administration should consider the option of striking and dismantling Iran’s ability to proliferate nuclear weapons, especially considering American officials believe Iran can build a bomb in roughly twelve days.

Lastly, strengthening alliances with regional partners (Egypt, Israel, Jordan, Pakistan, and Saudi Arabia, etc.) is another pivotal aspect of a comprehensive strategy that the Biden administration should pursue. Solidifying a unified front with its allies and friends in the Middle East fosters a collaborative approach to regional security. Collective efforts enable the sharing of intelligence, joint military exercises, and coordinated responses to potential threats. Such partnerships not only enhance the effectiveness of American actions but also contribute to regional stability by creating a cohesive and united response to aggression from Iran and its proxies.

Ultimately, well-defined red lines, coupled with a robust response to aggression, is essential for safeguarding American lives and maintaining stability in the Middle East. President Biden must seize the opportunity to demonstrate strength, resilience, and a commitment to protecting American interests in the face of escalating threats. If he fails to do so, deterrence will continue to falter, and attacks on American troops will continue to escalate. The stakes are high and clear red lines coupled with strict enforcement is the first step toward ensuring the US protects its interests within the region and enhances the credibility to deter further aggression.

 Aaron Holland is an Analyst at the National Institute for Deterrence Studies. The views expressed in this article are the author’s own.

Drawing a Clear Red Line: Biden’s Imperative Response to Iranian Aggression was originally published on Global Security Review.