Cleombrotus I in Wikipedia

Cleombrotus I (Greek: Κλεόμβροτος), (? - July 6, 371 BC), was a Spartan king of the Agiad line, reigning from 380 BC until 371 BC. Little is known of Cleombrotus' early life. He became king of Sparta after the death of his brother Agesipolis I in 380 BC, and led the allied Spartan-Peloponnesian army against the Thebans under Epaminondas in the Battle of Leuctra. His death and the utter defeat of his army led to the end of Spartan dominance in ancient Greece. Cleombrotus was succeeded by his son Agesipolis II.