That war is an evil is a proposition so familiar to every one that it would be tedious to develop it. No one is forced to engage in it by ignorance, or kept out of it by fear, if he fancies there is anything to be gained by it.

Book IV, 4.59-; "Nobody is driven into war by ignorance, and no one who thinks that he will gain anything from it is deterred by fear." (trans. Benjamin Jowett) - History of the Peloponnesian War