"So great are the psychological resistances to war in modern nations, that every war must appear to be a war of defence against a menacing, murderous aggressor. There must be no ambiguity about whom the public is to hate. Guilt and guilelessness must be assessed geographically and all the guilt must be on the other side of the frontier."

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Without doubt one is allowed to resist against the unjust aggressor to one's life, one's goods or one's physical integrity; sometimes, even 'til the aggressor's death... In fact, this act is aimed at preserving one's life or one's goods and to make the aggressor powerless. Thus, it is a good act, which is the right of the victim.

— Thomas Aquinas