The battle of Nomae (450 BC) was a defeat that reduced the power of Ducetius, king of the Sicels, and that eventually forced him into exile.
In this period eastern Sicily was split between the native Sicels, who mainly lived in the interior, and the Greeks, who had founded a series of cities around the coast. In the 460s the Greek cities had overthrown a series of tyrants, and Ducetius had taken advantage of this distraction to create a powerful Sicel league, with himself as its king. Most of his efforts had been aimed at fellow Sicels, and when he clashed with the Greek city of Catana in 461 BC it was as an ally of Syracuse.
In 451 BC Ducetius began a series of attacks on the Greeks. First he took Aetna, a city founded by colonists expelled from Catana in 461. He then turned to his west and besieged Motyum, in the territory of Akragas. Syracuse and Akragas raised armies and advanced to lift the siege, but they were defeated at the battle of Motyum (451 BC). The Syracusan commander was later executed for treason and both armies retreated to their homes. After the battle Motyum was captured by Ducetius.
In 450 BC both Akragas and Syracuse returned to the field. Ducetius had taken up a position at Nomae, possibly somewhere between Piazza Armerina and Barrafranca. This would have placed him somewhere to the east of Motyum, and to the west of his main powerbase.
The Syracusan army found Ducetius at Nomae. A fierce battle developed, with heavy losses on both sides, but eventually the Syracusans were victorious. The Sicel army dissolved, with most of the survivors seeking refuge in various strongholds. Ducetius's remaining supporters retreated to Motyum, but this stronghold was soon taken by Akragas.
Ducetius's support now drained away. Fearing that he would be seized by his own men he escaped from his camp and fled to Syracuse, where he threw himself on the mercy of the citizens. His plea was successful (probably because he offered to give Syracuse control of the lands that he still controlled), and he was sent into exile at Corinth.