I have very little patience for apologists for war, especially of the weak-kneed, unimaginative, "well, it's a fallen world, and so war is as inevitable as the dawn..." sort. I'm not an absolute pacifist, in the sense that I suppose that I could conjure a situation where war is necessary: I just think of pacifism as far and away the higher, more Godly way if resolving disputes.
Pacifism, to me, does not mean passivity or quietism in the face of evil - it means resisting evil through means other than violence.
The usual example of the "Good War" (despite the record of firestorms, atom bombs and assorted other appalling carnage) is World War II.
Well, WWII did not just "happen". The Nazis didn’t just “arise” in some pre-ordained, law-of-physics sort of way. They worked to gain power, using German’s (somewhat justified) resentment of having been assigned sole blame (and suffering under ruinous reparations) for the carnage of World War I.
European nations failed to recognize the danger posed by the rise of Hitler and the Nazis, and Germans allowed themselves to be seduced by the intoxicating brew of nationalism and self-exhaltation being peddled by Hitler and his minions.
None of that was inevitable: The allies could have been more humble and willing to accept more of the blame for WWI after their victory in 1918, and thus not impose such unfair and one-sided reparations upon Germany.
Germans could have resisted the temptation to give in to the Idolatry and self-glorification of nationalism, and instead worked to convince the victorious nations of the injustice of the Versailles armistice, through the non-violent means of appealing to their consciences.