They did to others that which they would not they should do to them — that grand principle of immorality upon which rests the whole art of war.

[Ils faisaient à autrui ce qu’ils ne voulaient pas qu’on leur fît, principe immoral sur lequel repose tout l’art de la guerre.]

Jules Verne (1828-1905) French novelist, poet, playwright

From the Earth to the Moon, ch. 10 (1865) [tr. Scribner’s (1890)]
    (Source)

Alt. trans.: "They did unto others what they would not have others do unto them, an immoral principle that is the basic premise of the art of war." [tr. Miller (1978)]