Robert Guiscard (gēskärˈ) [key], c.1015–1085, Norman conqueror of S Italy, a son of Tancred de Hauteville (see Normans). Robert joined (c.1046) his brothers in S Italy and fought with them to expel the Byzantines. In 1057 he succeeded his brother Humphrey as count of Apulia, and in 1059 Pope Nicholas II invested him at Melfi with Apulia, Calabria, and Sicily. However, most of these lands remained to be conquered, and Robert set himself to the task with the help of his younger brother Roger, who wrested (1061–91) Sicily from the Arabs (see Roger I). Calabria was occupied by 1060; Bari fell in 1071, Salerno in 1076. Robert's attacks on the duchy of Benevento, a papal fief, resulted in his excommunication (1074), but a reconciliation was brought about because the pope, Gregory VII, needed Norman assistance against Holy Roman Emperor Henry IV, who had invaded Rome (1081). Ultimately, virtually all of Benevento except the city itself fell to Robert; he then turned his eyes to the Byzantine Empire. Championing the cause of the deposed emperor, Michael VII, he sailed in 1081, conquered Corfu, and defeated (1082) Emperor Alexius I. In 1083 he returned to aid Gregory VII, who was besieged in the Castel Sant' Angelo. Robert's troops sacked Rome for three days (1084), but were again expelled by those of Henry IV. Robert, with his elder son Bohemond I, resumed his conquests in the east. Robert died of fever during the siege of Cephalonia and was succeeded in Apulia by his younger son, Roger.
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