The title of "king of Jerusalem" was also continuously used by the Angevin kings of Naples, whose founder, Charles of Anjou, had in 1277 bought a claim to the throne from Mary of Antioch. Thereafter, this claim to the Kingdom of Jerusalem was treated as a tributary of the crown of Naples, which often changed hands by testament or conquest rather than direct inheritance. As Naples was a papal fief, the Popes often endorsed the title of King of Jerusalem as well as of Naples, and the history of these claims is that of the Neapolitan Kingdom.