any authority north of the Alps. When Berengar I of Italy was assassinated in 924, the last nominal heir to Charlemagne was dead and the imperial title was left unclaimed. King Rudolf II of Upper Burgundy and Hugh, Count of Provence, the effective ruler of Lower Burgundy, competed with military means to gain dominion over Italy. In 926, Hugh's armies defeated Rudolf, Hugh could so establish de facto control over the Italian peninsula and had himself crowned as King of Italy. His son Lothair was elevated to co-ruler in 931. Hugh and Rudolf II eventually concluded a peace treaty in 933; four years later Lothair was betrothed to Rudolf's infant daughter Adelaide. In 940, Berengar II, Margrave of Ivrea, a grandson of former King Berengar I, led a revolt of Italian nobles against his uncle Hugh. Forewarned by Lothair, Hugh exiled Berengar II from Italy, and the margrave fled to the protection of Otto's court in 941. In 945, Berengar II returned and defeated Hugh with the support of the Italian nobility. Hugh abdicated in favor of his son and retired to Provence; Berengar II made terms with Lothair and established himself as the decisive power behind the throne. Lothair married the sixteen-year-old Adelaide in 947 and became nominal king when Hugh died on 10 April 948, but Berengar II continued to hold power as mayor of the palace or viceroy. Strategical marriage to Adelaide, Queen of Italy Lothair's brief "reign" came to an end with his death on 22 November 950, and Berengar II was crowned king on 15 December, with his son Adalbert of Italy as co-ruler. Failing to receive widespread support, Berengar II attempted to legitimize his reign and tried to force Adelaide, the respective daughter, daughter-in-law and widow of the last three Italian kings, into marriage with Adalbert. Adelaide fiercely refused and was imprisoned by Berengar II at Garda Lake. With the help of Count Adalbert Atto of Canossa, she managed to escape from imprisonment. Besieged by Berengar II in Canossa, Adelaide sent an emissary across the Alps seeking Otto's protection and marriage. A marriage to Adelaide would have strengthened the king's position to claim the Italian throne and ultimately the emperorship. Knowing of her great intelligence and immense wealth, Otto accepted Adelaide's marriage proposal and prepared for an expedition into Italy. First Italian Military Expedition In the early summer of 951, before his father marched