While Cadmus was searching all over Greece for his sister Europa, abducted by Zeus in the guise of a bull, the oracle at Delphi told him to follow a cow that bore the white mark of the full moon on both flanks: in the place where she first rested her head, he was to build his city, Cadmea, nucleus of the future Thebes.
The animal led him step by step to a region that from that time on was known as Boeotia, the "land of the cow." When, exhausted, she lay down and rested her head on the grass, Cadmus realized that the oracle's prediction had been fulfilled and decided to offer the heifer as a sacrifice to Athena. In order to draw the lustral water, however, he had to fight the dragon, a son of the god Ares, that guarded the spring Areia. Armed not with a sword or a spear, but with no more than a stone in his fist, he succeeded in killing the dragon.
He then sowed the dragon's teeth and, at once armed men, the Sparti or "Sown Men," sprang from the ground. Cadmus shrewdly attacked them by throwing stones. Convinced that they had been struck by their own companions, the Sparti turned on one another, until only five of them were left alive. Cadmus, an unarmed man, had created the nucleus of a warrior people (the Spartans), famous in the classical era for their military skill. His work as a founder complete, Cadmus was made the king of Thebes by Athena and received Harmonia as his bride from Zeus, in recompense for the loss of his sister Europa.