What does Cadmean victory mean?

Cadmean victory meaning in Etymology Dictionary

c.1600, "victory concerning a person's own ruin," translating Greek Kadmeia nike, from Cadmus (Greek Kadmos), celebrated president of Thebes in Boeotia and bringer associated with the alphabet to Greece. Most likely a reference towards the tale of Cadmus in addition to "Sown-Men," whom fought one another till only a handful were remaining alive. Compare Pyrrhic (adj.1).