Pyrrhus, a third-century BC king of Epirus (which covers today's Albania and northwestern Greece), wanted to save the Greek colony of Tarentum in southern Italy from being absorbed by the Roman Republic. Presenting himself as a defender of Greek liberty, he invaded Italy with at least 25,000 men.
....near Heraclea a Greek and Roman army met for the first time. The Roman legion was a more flexible weapon than the cumbersome phalanx, but the tactics of Pyrrhus and his elephants won him the victory--but a costly one....During this time the Tarentines had grown weary of the military obligations imposed on them by the king, to whom they had accorded full powers for the duration of the war*.
At length the Carthaginians grew alarmed at Pyrrhus' rampages, and cooperated with the Romans (!) to drive his forces out of Sicily and Southern Italy.
*Jean Hatzfeld, History of Ancient Greece, Chapter 30