Pietro IV Candiano (925–976) was the twenty-second (traditional) or twentieth (historical) doge of Venice from 959 to his death. He was the eldest son of Pietro III Candiano, with whom he co-reigned and whom he was elected to succeed. Rise Pietro was appointed co-doge by his father. However, towards the end of his father's dogeship, Pietro IV revolted against him, but failed thanks to popular support for the doge. Pietro III pleaded for his son's life and managed to prevent his execution, but could not stop his exile. The rebellion of Pietro IV was probably related to the situation in Italy at the time. Pietro IV had supported Berengar II, the Frankish king of Italy, while his father pursued a neutral policy. Berengar II's Kingdom of Italy was taken over by Otto I (who would later become Holy Roman Emperor) in 952. Berengar swore loyalty to Otto I, who gave him back the title of king of Italy as vassal king. Berengar later revolted against Otto, attacking the March of Verona and invading the Papal States. The exiled Pietro IV went to Ivrea, where the margrave, Guy of Ivrea took him to his father, Berengar II. He then joined the military campaigns which Adalbert, the son of Berengar II, and Hubert, were conducting against Theobald II, Duke of Spoleto and Camerino. Berengar II allowed Pietro to conduct military operations in Ravenna. With six ships from Ravenna, he captured seven Venetian ships. He returned to Venice when his father died, two and a half months after he had been exiled. Dogeship When Pietro III died in 959, Pietro IV surprisingly became the next doge. Probably due to the turbulent recent past, Pietro imposed an oath of loyalty to his power, which was not a Venetian custom. It was probably an import from the mainland. He resumed Venice's relationship with the Byzantine Empire, which his father had interrupted. He renewed a ban of the slave trade. His ban was with regard to this trade with the Byzantines. No Venetian could lend money to them which would be used to buy slaves, transport slaves to their territories or receive money from them to carry slaves. In a nepotist move, Pietro had the rival candidate to the position of Bishop of Torcello accused of simony, blinded and expelled so that he could install his brother Vitale to this bishopric. In 969 he procured him