I thought it it might be helpful to look at the current war in Ukraine in terms of what philosophers and theologians call Just War theory.
From the time of Augustine (c.400 A.D.) many Christian philosophers and theologians have thought about the question of the demands and restrictions the Gospel imposes on the use of force.
One result of that thinking has been a list of criteria that must be satisfied in any situation in which force, particularly military force, is contemplated. This is called jus ad bellum (justice in going to war).
These criteria generally include the following:
1. Just cause. Examples of a just cause for the use of force include: Defense against an unjust invader; Protection of family, home, or other innocent victims from direct harm; Recovery of goods unjustly taken; Protection of constitutional rights and liberties from government encroachment; Defense of allies who have been unjustly attacked, etc.
2. Just intent. The purpose of the war must be to establish peace or to protect the innocent. Hatred, economic gain, or the exercise of power are all illicit reasons for using force against another.
3. Legitimate authority. The war must be declared/waged by a legitimate government authority. A war declared by a terrorist organization like ISIS is by definition unjust.
4. Reasonable prospect of success. Deliberately protracted wars or wars initiated with no reasonable hope of success are unjust.
5. Last resort. When it's clear that no measure short of the application of force will avail, or that an attack upon one's nation is imminent, war is justified provided the other criteria are met. This requirement is problematic in that it's always possible to imagine yet another set of peace talks, etc. that could be embarked upon and which would delay war indefinitely.
Thus, governments have to exercise reasonable judgment in determining whether they have actually exhausted all practical options and have been left with no realistic alternative to war.
Just War theory also requires that wars not only be warranted by these stringent criteria (jus ad bellum) but that when fought they be conducted according to certain guidelines (jus in bello: justice in war). The two chief criteria of jus in bello are:
1. Discrimination. Civilians should never be deliberately targeted. This follows from the Christian imperative to be compassionate and merciful. It entails that prisoners not be mistreated and that property and livelihoods not be unduly or unnecessarily damaged.
2. Proportionality. The means employed must be no more brutal or violent than what is necessary to secure victory. It would be unjust to slaughter defeated and retreating enemy soldiers if they no longer pose a threat. It would be a disproportionate response, and therefore unjust, to respond to a cross-border raid with nuclear weapons.
As is no doubt obvious, the heat and stress of war and incipient war may create a lot of gray areas for those seeking to hold to the criteria of Just War, and there's often much room for differences in interpretation. Nevertheless, those who wish to wage war justly will strive to hew as closely to these principles as the exigencies of war permit.
Even so, I think it's clear to anyone who's been following the war in Ukraine that Russia is waging an unjust war. They fail the jus ad bellum test, particularly criteria #1,2 and 5, and they also fail the first criterion of the jus in bello test. The response of the Ukrainians is compatible with criteria #1,2,3, and 5 of the jus ad bellum test and #1 of the jus in bello test.
None of the other criteria really apply to their struggle.
The Russians from Vladimir Putin on down to those infantry troops who are shooting and raping civilians are war criminals, and one hopes that the world will not forget their crimes and return to the status quo ante once this conflict is over.
Those responsible for the death, terror and destruction visited upon the Ukrainian people should remain international pariahs as long as they live and as long as history is written.
