War happens. It is never desirable or beneficial. Too many innocents die, property is wasted, hatreds and feuds are prolonged, and we accustom ourselves to beastly behavior. There is no place in the Buddhist concept of “nobility” for war. It is never morally legitimate. It isn’t even a “necessary evil.” It is merely the bad policy of shortsighted, cowardly, selfish, and ill-informed leadership.
So when the UK fought against Nazi Germany this act was "merely the bad policy of shortsighted, cowardly, selfish, and ill-informed leadership."
When Vietnam invaded Cambodia to destroy the Khemer Rouge, this act was "merely the bad policy of shortsighted, cowardly, selfish, and ill-informed leadership.
Need I go on?
Sometimes violence is necessary, why else would we (and all other life) have evolved to make use of it?