Cadmean victory (n.) Look up Cadmean victory at Dictionary.com
c. 1600, "victory involving one's own ruin," translating Greek Kadmeia nike, from Cadmus (Greek Kadmos), legendary hero-founder of Thebes in Boeotia and bringer of the original sixteen-letter alphabet to Greece. Probably a reference to the story of Cadmus and the "Sown-Men," who fought each other till only a handful were left alive. Compare Pyrrhic (adj.1).