By early 237 BC, after numerous setbacks, the rebels were defeated and their cities brought back under Carthaginian rule. An expedition was prepared to reoccupy Sardinia, where mutinous soldiers had slaughtered all Carthaginians. However, Rome declared that this would be an act of war and occupied both Sardinia and Corsica, in contravention of the recent peace treaty. This has been considered to be the single greatest cause of war with Carthage breaking out again in 218 BC in the Second Punic War.