Peace cannot be kept by force. It can only be achieved by understanding. You cannot subjugate a nation forcibly unless you wipe out every man, woman, and child. Unless you wish to use such drastic measures, you must find a way of settling your disputes without resort to arms.
Albert Einstein, in a speech to the New History Society (14 December 1930), reprinted in "Militant Pacifism" in Cosmic Religion (1931)