After the defeat of Hicetas at Adranum by Timoleon, Mamercus joined Timoleon and concluded a treaty of alliance with him. 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. At first they achieved a partial success, cutting to pieces a body of mercenaries in the Syracusan service. But Hicetas was defeated by Timoleon and fell into his hands, after which Timoleon marched against Catane. Mamercus met him in the field, but was defeated with heavy loss. So the Carthaginians concluded a peace with Timoleon.