Many arguments have been advanced attempting to create a just war theory, from Blessed Augustine of Hippo to the Latins’ Thomas Aquinas (of whom there are Orthodox readings - sorta). Their arguments essentially argue from a position of war’s inevitability and do attempt to defend war as just when it’s defensive, when waged by wise men, that it be under the orders of a rightful sovereign, and only as a last resort. Nonetheless, we in the Eastern tradition find this troubling.
While wars may be inevitable, we are reminded that these are fathers and sons, husbands and brothers that are fighting; in the current situation in the Ukraine this is especially true, and several of our hierarchs have called for an end to the fratricide taking place. We believe that no wars are just, nor can any killing be rightly defended before God as being unsinful - all killing is inherently sinful, and we are subject to repentance. St. Basil the great tells us that even defensive wars or the protecting of the weak and innocent are themselves never justifiable. This is one of the reasons clergy are forbidden in the canons from holding political office and from spilling blood - more on that in another Ask the Priest…