The morally right course of action for the Ukrainians, according to just war criteria, is not clear. And doubt should be the mother of caution, not of recklessness – or even of courage

During his recent visit to Malta, Pope Francis requested prayers for “martyred Ukraine”. This was a striking image to choose, not least because in the Christian tradition one thing that defines a martyr is lack of physical resistance, modelled on Christ’s not resisting arrest in the Garden of Gethsemane: “Put your sword back into its place, for all who draw the sword will die by the sword” (Matthew 26:52).

Since the Russian invasion, Ukrainians have courageously resisted those infringing their country’s sovereignty and the Russian Federation has violated countless norms of international law and Christian teaching about war. But is armed self-defence in these circumstances morally justifiable? Does armed resistance have a “reasonable chance of ­success”? Is it “proportionate” in terms of the evils it seeks to avoid?