history consists of "wars to end all wars", "wars to punish aggressors" and alikes, not a single of them actually worked at stopping future wars. On the other hand just giving in, like many did to Romans, or Mongols, not too infrequently led to centuries of peace.

How do "wars to stop the invaders looting your stuff, killing most of your menfolk, raping your women and eating your lifestock" fit in here?

You have a strange idea of 'just' if it doesn't include a nation defending itself from attack (war) ever.