With Roman backing he established his own kingdom of Numidia, west of Carthage. All of this happened in accordance with Roman interest, as they wanted to give Carthage more problems with its neighbours. Under Masinissa many of the semi-nomadic tribes became peasant farmers. Still, there were few urbanized areas in Masinissa's Numidia.
All through his life Masinissa extended his territory, and he was cooperating with Rome when towards the end of his life he provoked Carthage to go to war against him. This gave Rome an excuse to declare war against Carthage, and started the 3rd and last Punic War. At his death, Numidia was divided into kingdoms ruled by his sons.