Robert (born 1278—died Jan. 19, 1343, Naples) was an Angevin prince and Guelf (papal party) leader who ruled Naples as king for 34 years (1309–43).
Robert’s early years were clouded by the War of the Sicilian Vespers (1282–88), in which his father, Charles II of Anjou, was taken prisoner by the Aragonese. By the terms of the treaty Charles was freed, and Robert took his place as hostage at the Aragonese court. Taking the title of duke of Calabria (1296), he led an expedition attempting to recover Sicily from the Aragonese prince who ruled it as Frederick III. Robert’s military success produced the Peace of Caltabellotta (1302), by which the Aragonese agreed to return Sicily to the House of Anjou when Frederick died.
On the death of his father in 1309, Robert inherited Naples and extensive territories in northern Italy and southern France. For several years Robert skirmished politically and militarily on the side of the Guelf party in northern Italy against the Ghibelline (pro-imperial) faction led by the Visconti of Milan, whom he defeated at Sesto, west of Genoa, in 1319. His desire to enlist the interest of Pope John XXII in a final defeat of the Ghibellines of northern Italy caused Robert to take up residence at Avignon, the papal seat, but in 1324 the victory of the Visconti over Guelf forces at Vaprio, east of Milan, brought him back to Italy to defend his lands.
Robert remained neutral when the German king Louis the Bavarian marched into Italy, was crowned emperor in Rome as Louis IV (1328), and set up an antipope, Nicholas V. Relations between Robert and John XXII terminated when the Pope allied himself with King John of Bohemia, who invaded northern Italy in 1330. In return for King John’s support, the Pope offered him Robert’s territories in southern France. The Pope’s diplomacy shattered the traditional Guelf–Ghibelline alignments in Italy, and the league that Robert joined, consisting of members of both parties, drove King John out of Italy in 1336. The final years of Robert’s reign were marked by defections of his northern Italian towns, and his failure to regain Sicily after Frederick III’s death in 1337 brought a steady decline of Angevin power and influence.