So, when I apply this principle—

a method which rejects revenge, aggression and retaliation.

to this—

War is a necessary evil

This is what I get:

We should not retaliate against those who wage war against us or seek revenge. Nor should we start the war, even as a preemptive strike against what we determine to be a devastating or extinction level attack.

I'm in agreement that we should not start wars. I'm also in agreement that a war should not be entered solely as a matter of revenge or retaliation.

But I do believe in self-protection. So, while agreeing that war is not a necessary evil for the reasons stated above, I'm hoping this leaves room to defend ourselves against an aggressor. Which means, in my mind, repel the attack until it's no longer a threat, then stop.

If this was implied somehow, I apologize for missing it. If it's supposed to mean no self-defense, then I'd like to know what that's supposed to look like.