Here are a few Friedrich Nietzsche quotes on war from his book Thus Spoke Zarathustra.
“War and courage have done more great things than charity. Not your sympathy, but your bravery hath hitherto saved the victims.”
“If one would have a friend, then must one also be willing to wage war for him: and in order to wage war, one must be capable of being an enemy.”
“That there is struggle and inequality even in beauty, and war for power and supremacy: that doth he here teach us in the plainest parable.”
“No one ever spake such warlike words: ‘What is good? To be brave is good. It is the good war that halloweth every cause.'”
Keep in mind that much of what Nietzsche spoke of was in reference to internal wars, as much as external ones.