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). Guido Mor disagrees with this interpretation. He thinks that the links Pietro had with Berengar II, especially those with Waldrada's father, when he was in exile (see above) initially made an alliance with Otto I unlikely. He points out that Waldrada's father had been hostile to Otto I during his second expedition and had to flee in 962-63 and suggests that Pietro's second marriage might have taken place then, in 962–63, and that it sealed his support to Otto's opponents. He also argues that Otto's mentioned grants were to people Pietro had alienated. Giovanna, as a repudiated wife, must have been hostile to Pietro. Mor also thinks that the mentioned Vitale Candiano was not Pietro's brother, but