Perpetual peace is a dream, and it is not even a beautiful dream. War is an element in the order of the world ordained by God. In it the noblest virtues of mankind are developed; courage and the abnegation of self, faithfulness to duty, and a spirit of sacrifice: the soldier gives his life. Without war the world would stagnate, and lose itself in materialism.

Letter to Johann Kaspar Bluntschli [December 11,1880]