Nicomedes was the son of
Cleombrotus (died 479 BC), who was appointed
regent of Sparta after the death of his brother
King Leonidas (reigned 489–480 BC) at the
Battle of Thermopylae. During this time, Leonidas' son
Pleistarchus (reigned 480–458 BC) was not yet of age to rule. When Cleombrotus died, he was succeeded by his son
Pausanias (died 477 BC). Pausanias was starved to death by the Spartans on suspicion of treachery. Pleistarchus was succeeded by Pausanias' son Pleistoanax (reigned 458–409 BC). He too was a minor when he became king, and Nicomedes was appointed regent. The
First Peloponnesian War, between Sparta and its allies (including
Thebes; the
Peloponnesian League) and
Athens and its allies (including
Argos; the
Delian League), had broken out in 460 BC. When the
Phocians attacked the
Doris, which was considered the homeland of the
Dorians of Sparta, the Spartans retaliated. Nicomedes was given command of this campaign, in place of the king. The army, which consisted of 1,500 Spartan and 10,000 allied
hoplites, was sent north. ==References==