Ukraine - is it a Just War?

Traditional just war theory works from a polite fiction, it tells us that wars can be judged by two separate questions, one is about whether the decision to fight is just and the other is about how the fighting is carried out. Crucially, it claims that the soldiers on each side share a kind of moral equality. They are all doing their duty, so they can kill each other without either side being condemned as murderers. The rights and wrongs are pushed upwards to the leaders, and the battlefield becomes a zone of suspended moral judgement.

Jeff McMahan is a leading philosopher of war and moral responsibility, best known for his revisionist just war theory. McMahan contributes to the Philosophy or War by rejecting that whole structure, and the war in Ukraine shows why he thinks it collapses. He insists that soldiers are not morally interchangeable, and that those fighting an unjust war bear moral responsibility for their participation. He does not subscribe to the idea that two sides can fight with the same moral standing when one has crossed a border to seize territory and the other is trying not to be conquered. He treats the Russian invasion as a straightforward act of aggression. No layers of historical blame, no puzzles about who provoked what. Just an unjust use of force aimed at domination.

Once that is established, McMahan removes the equal moral standing of the combatants. Russian soldiers are not simply neutral instruments of policy. They are agents participating in an unjust enterprise. Ukrainian soldiers are not just one set of troops among others but individuals resisting an aggression. The field is not ethically level, and pretending it is only excuses the aggressor. He still puts limits on what Ukraine may do. A just cause does not turn into a licence for every method. He insists that Ukraine must fight in a way that remains proportionate, and he is particularly wary of anything that drags the conflict into catastrophic escalation. Even aims that feel intuitively righteous, like pushing Russian forces out of every occupied region, become morally complicated if the price is a level of destruction out of all proportion to what would be gained.

He extends the argument to civilians. Some Russians who cheer on the war are not morally untouched by it, and he allows that sanctions and other non violent pressures can legitimately fall on them if there is a genuine prospect of shortening the conflict. But that does not open the door to targeting civilians with violence. He holds the line against retaliatory strikes on civilian areas in Russia, even when Russia has done exactly that to Ukraine. For him, answering terror with terror is not defence. It is moral drift.

The picture he draws is not sentimental. It does not pretend everyone means well or that the truth lies somewhere in the middle. Russia is in the wrong. Ukraine is resisting. The justice is one sided. But the moral limits stay in place because without them the distinction between defender and aggressor starts to dissolve, and once that happens the whole moral case collapses into the kind of cynicism that just war theory was invented to prevent.