Just war theory and why Ukraine has a right to defend itself

The ethics of self-defence and the duty to take up arms in the face of aggression.

Ignoring the signs: a woman walks through war-torn central Kyiv - Photo: CNS/Reuters, Gleb Garanich

Two Catholic moral theologians consider the ethics of taking up arms in self-defence against an overwhelmingly superior military force. 

The courageous and inspirational Ukrainians are responding to Russia’s invasion of their country with both nonviolent and armed resistance. We watch on our mobile phones with anguish and concern as Ukrainian civilians in the city of Melitopol plant themselves in front of armoured military vehicles with astonishing courage, shouting “Murderers!” and “Occupants!” as Russian soldiers fire gunshots into the air. At the same time, we watch as Russian citizens march through their cities chanting “No More War!”, bravely risking arrest and long prison sentences. Civil resistance is alive in Ukraine. Civil disobedience is alive in Russia.

Nonviolence, as Pope Francis has emphasised, is central for Catholics. Beside its shameful complicity in war and conquest, Christianity can claim a long tradition of nonviolent resistance to injustice, from Jesus turning the tables of the money changers in the Temple marketplace and the refusal of early Christian martyrs like Ss Perpetua and Felicitas to honour Roman imperial gods, to the peace witness of Menno Simons during the Reformation-era religious wars, to modern faith-based activists who have joined with ­others to resist apartheid in South Africa, racism in the US, corruption in the Philippines and tyranny under the communist bloc.

Christian ethics prescribe nonviolent expressions of resistance as the primary response to injustice. As disciples of Jesus, the “rabble-rouser”, we have a duty to protest injustice and support those who use the tools of nonviolent resistance against aggressors and warmongers. The nonviolent demonstrations in both Ukraine and Russia against the war are also a powerful reminder of a core principle of just governance, since at least the time of Thomas Aquinas: the government belongs to its people to secure the common good. This idea is one that Ukrainian President Volodymyr Zelenskiy accepts and protects; and one that Russian President Vladimir Putin does not. 

Ukrainians are also responding to the aggression unleashed by President Putin with armed resistance. As Ukrainian refugees board trains bound for Poland and other safe havens, brothers, husbands, fathers and uncles are absent. Under the state of emergency, Ukrainian law prevents men aged 18 to 60, who could be conscripted, from crossing the ­borders. Most seem willing to take up arms against the Russian military. Are they wrong to do so?

The just war tradition is anchored in the principle of neighbour-love, which calls us to imitate the Good Samaritan and be the neighbour who acts out of love for those in dire need and distress (Luke 10:25-37).

As the twentieth-century Methodist ethicist Paul Ramsey asked, had the Samaritan arrived upon the scene while the crime was in progress, what might he have done? We think that he would, if possible, have intervened nonviolently; if necessary, though, perhaps he would have used force.

Ukraine has been invaded and its cities are being bombed into submission. It certainly has just cause and legitimate authority to resort to armed resistance in self-defence.

But is there a reasonable hope, or probability, of success? The just war tradition prohibits engaging in warfare that one knows to be futile, which would just be a wasteful spilling of blood. The Russian military’s resources and capacities far exceed that which the Ukrainians could reasonably expect to defeat, and Nato does not intend to send ground troops to wage war alongside the Ukrainian defence forces. And while the Ukrainians are desperately urging the West to establish a no-fly zone, so far our solidarity and sympathy with their just cause is outweighed by the concern that this would draw the Nato nations into war with Russia.

So does the Ukrainian armed resistance against Putin’s war of aggression still meet the criterion of a “just war”? Consider the context in which the criterion of “reasonable hope of success” was first established. Its development is credited to the sixteenth-century Spanish Jesuit Francisco Suárez as a response to the Italian Dominican, Tommaso de Vio Cajetan. Suárez was associated with the neo-Thomistic intellectual tradition known broadly as the School of Salamanca. Cajetan asserted that war is so destructive that nations are obligated to refrain from it unless they can be certain of victory. Suárez disagreed. Not only did he think it impossible to be sure which side will prevail in a military engagement, he also ­worried that accepting Cajetan’s “certainty of success” criterion would mean that mightier nations would have free rein to annex, invade, and overrun weaker ones. In fact, Suárez ­considered it a duty of rulers, whose job is to maintain peace and justice for common good, to take up arms in national defence in the face of ­aggression.

Ukraine has a right to defend itself. Not only is nonviolent resistance by citizens and others to an unjust and immoral invasion justified, but, in our view, with the outcome of the conflict still uncertain, armed resistance is also justified. Of course, Ukraine must abide by the principles of how a just war should be conducted that are enshrined in international law, including right intention towards establishing a just peace; not deliberately targeting civilians; and the humane treatment of prisoners of war. As for Nato’s responsibility, not only to its member nations’ citizens but also to neighbouring Ukrainians, we fervently pray for the virtue of prudence; as the Catechism says: “The evaluation of these conditions for moral legitimacy belongs to the prudential judgement of those who have responsibility for the common good.”

Anna Floerke Scheid is associate professor of theology at Duquesne University and author of Just Revolution: A Christian Ethic of Political Resistance and Social Transformation. Tobias Winright is associate professor of theological and health care ethics at Saint Louis University and associate member of the Las Casas Institute for Social Justice, Blackfriars Hall, Oxford. His publications include After the Smoke Clears: The Just War Tradition and Post War Justice.