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.
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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 the Patriarchate of Grado, the most powerful ecclesiastic position in the duchy of Venice.
Pietro destroyed Oderzo, which controlled the routes towards northern Europe. He subdued Ferrara, which was emerging as the main trade centre in the area of the River Po and competed with Venice over trade in this area.
For political reasons, Pietro repudiated his first wife, Giovanniccia, forcing her into the monastery of San Zaccaria. He had a son with her, Vitale. In 966, Pietro remarried to Waldrada, the daughter of Hubert, the marquis of Tuscany, and a cousin of the wife of the emperor Otto I. As the most powerful woman in Italy, Waldrada brought Pietro a large dowry both in money and properties in Friuli, the March of Treviso, Andria and the Ferrara area. The location of these properties is unclear.
Pietro's actions were probably related to the changing political situation in Italy. In 961/64 Otto I had made a second expedition to Italy, took the title of king of Italy, defeated Berengar II and imprisoned him in 963. In 966 Adalbert, the son of Berengar, rebelled but was defeated. Otto I was firmly in charge of Italy. Betrolini notes that various historians think that there was an alliance between Otto I and Pietro IV and that this is indicated by Pietro's marriage to Waldrada, a relative of Otto, and the fact that in 963 Otto I confirmed the monastery of San Zaccaria's property in the county of Padua in favour to its abbess Giovanna, who was probably Pietro's first wife, and granted tax assets in the county of Treviso to a Vitale Candiano, whom they identify as Pietro's brother (both counties were in the Kingdom of Italy).
Death
In 976 the Doge's Palace was attacked. Since the palace was like a fortress, it was set alight. The doge was forced to come out and he was killed, together with his young son Pietro by Waldrada, by some notables (among whom there were some of his relatives). Their bodies were thrown in the slaughterhouse, but were later recovered and buried in the monastery of Sant'Ilario, in Fusina, on the mainland coast of the Lagoon of Venice, perhaps because Pietro owned large estates in the area. Two previous doges, Agnello e Giustiniano Partecipazio, who founded the monastery, were also buried there.
As the fire spread, some 300 buildings were destroyed, including the churches of St Mark's, the old San Teodoro, and the newly completed Santa Maria Zobenigo.
Waldrada managed to escape the attack, taking her young daughter Marina with her. She fled to the empress Adelaide, the mother of the new emperor, Otto II, in Verona. She appealed to Otto II to set fire to Venice and imprison its people. She demanded the reconstitution of her dowry. The new doge, Pietro I Orseolo, sent an envoy to Piacenza to discuss her claim with Otto II. These were amended in a way that satisfied both parties (Pietro IV had introduced the Mundio, a custom which was new in Venice, in which the doge conferred one fourth of his personal assets to his wife; Venice had confiscated Pietro's freehold estates). Waldrada issued a receipt (carta securitatis) to the new doge and the Venetian people.
Marina married Tribuno Memmo, who was doge in 979–991.




