These Campanians could see no reason why a band of mercenaries should not seize on their own behalf any city entrusted to their guardianship, provided only they were in a position to hold it--the Samnites had established their dominion in Capua itself, and the Lucanians in a succession of Greek cities, after a fashion not much more honourable.
Mammertines Nowhere was the state of political relations more inviting for such enterprises than in Sicily.

Already the Campanian captains who came to Sicily during the Peloponnesian war had insinuated themselves in this way into Entella and Aetna.

Somewhere about the year 470 a Campanian band, which had previously served under Agathocles and after his death (465) took up the trade of freebooters on their own account, established themselves in Messana, the second city of Greek Sicily, and the chief seat of the anti-Syracusan party in that portion of the island which was still in the power of the Greeks.

The citizens were slain or expelled, their wives and children and houses were distributed among the soldiers, and the new masters of the city, the Mamertines or "men of Mars," as they called themselves, soon became the third power in the island, the north-eastern portion of which they reduced to subjection in the times of confusion that succeeded the death of Agathocles.

The Carthaginians were no unwilling spectators of these events, which established in the immediate vicinity of the Syracusans a new and powerful adversary instead of a cognate and ordinarily allied or dependent city.