When Timoleon had not only made himself master of Syracuse, but defeated the Carthaginians in the great Battle of the Crimissus (339 BC), Mamercus became apprehensive that his ally's object was nothing less than the complete expulsion of all the tyrants from Sicily.
In consequence, Mamercus entered into a league with Hicetas and the Carthaginians to oppose Timoleon's progress.
Abandoned by his allies, Mamercus saw little chance of success and fled to Messana, where he took refuge with Hippo [es], tyrant of that city.
Timoleon, however, quickly followed him and laid siege to Messana, both by sea and land, forcing Hippo to flee.
[2] Cornelius Nepos hints that Mamercus was not a Sicilian by birth, but had first come to the island as a leader of Italian mercenaries.