Just War Theory and Cyberwar

cyber war

Just War Theory and Cyberwar

By Luke Perez, Ph.D.

Cyberwar, to paraphrase Carl von Clausewitz are acts of force to compel the enemy to do one’s will through electronic, or virtual means by the use of malicious code (On War, 75). The idea that computers will contribute to, or even take over war, is as old as computers themselves (e.g., one thinks of the 1983 film, War Games). In the last decade, however, cyberwar has come into widespread use. Some of the well-known instances of cyberattacks in world affairs include the attacks on Estonia (2007), the Stuxnet worm which targeted the Iranian nuclear program (2010), and the hacking of the Democratic National Committee (2015–2016).

The increasing frequency and complexity of cyberattacks as instruments of war and geopolitics has led many to wonder whether the just war tradition is adequate to the task of developing moral guidelines for the proper use of, and response to, cyberwarfare. The doubts are misplaced if understandable. Every new technological advancement risks undermining our ethical thinking, inviting both abuse and neglect of morality in politics. Cyberwar is no different and among its many novelties, its ability to scale up and down the chain of escalation seems to be unique to it: cyberattacks can run the gamut of small, microtactical efforts at espionage from non-state actors, to full-scale strategic “first strikes” which will precede or accompany other military uses of force.

Thankfully, the just war tradition is more than adequate for dealing with the novel challenges unique to cyberwar. The clearest exposition of the tradition from the ancients to the high point of Christianity is, of course, found in Thomas Aquinas’ treatment of the topic in the Summa Theologiae (II-II Q 40). In Thomas formulation, only three criteria are needed to determine whether a war is just. The decision to wage war must be made by a public authority, not private actors; it must be for a just cause; and those waging and fighting the war must have the right intention (peace, rightly understood).


What is not found in Thomas’ formulation is any treatment of the jus ad bello and jus in bello. The absence of those secondary categories proves helpful to those thinking through the challenges of cyberwar. It is not anything inherent to cyber, nor any tool of war, that determines whether something is just or unjust in war. Rather, it is the formal disposition and judgement of the human persons making decisions whether, and how, to make war. By first working through the Thomistic model of just war, policymakers and ethicists can more easily apply the ad bello and in bello criteria because the questions proper to those categories concern the prudential application of warfare, not whether a war can be just.

All this is not to say that cyberwar lacks any serious challenge to the tradition. There are several but two stand out as needing the immediate attention of anyone thinking through the ethics of cyberwar. First, thinking of war in legalist terms will lead to an atrophy of the tradition. The legal framework creates new criteria, rules, procedures to adapt to new technology. But the result is a framework that becomes too complex and so is ignored.

Likewise, a too cavalier endorsement of cyberwar as just on the grounds that it does not cause harm in the way that guns and munitions do invites moral hazard. Cyberwar seems to give policymakers “more options” to use coercive power without the sunk costs and high risks of putting boots on the ground. But if they rely too quickly and too frequently on cyberwar, they may paradoxically start a sequence of escalation that commits nations to war when none would have otherwise occurred.

To conclude, ethicists and strategists are wise to consult the just war tradition as they deal with the problems of cyberwar. A classical approach found in Saint Thomas is a great place to begin such reflections, especially for those in government because the mental model is more easily grasped. Cyberwar brings new puzzles, but as human nature has not changed, the just war tradition is worthy guide for thinking about the place of cyberwar in the quest for that elusive lasting peace among mankind.

Luke Perezluke-perez is an assistant professor in the School of Civic and Economic Thought and Leadership at Arizona State University. His research investigates religion, ethics, and American foreign policy.