Berengar then assumed the royal title with his son
Adalbert as co-ruler and were crowned in
Pavia, in the
Basilica of San Michele Maggiore. He attempted to legitimize his kingship by forcing Lothair's widow
Adelaide, the respective daughter, daughter-in-law, and widow of the last three Italian kings, into marriage with Adalbert. However, the young woman fiercely refused, whereafter Berengar had her imprisoned at
Garda Castle, allegedly mistreated by Berengar's wife Willa. With the help of Count
Adalbert Atto of Canossa she managed to flee and entreated the protection of King Otto of Germany. Otto, himself a widower since 946, took the occasion to gain the
Iron Crown of Lombardy: Adelaide's requests for intervention resulted in his 951 invasion of Italy. Berengar had to entrench himself at
San Marino, while Otto received the homage of the Italian nobility, married Adelaide himself, and assumed the title of a
King of the Lombards. He afterwards returned to
Germany, appointing his son-in-law
Conrad Italian regent at Pavia. Berengar by Conrad's agency appeared at the 952
Reichstag in
Augsburg and paid homage to Otto. He and his son Adalbert remained Italian kings as Otto's
vassals, though they had to cede the territory of the former
March of Friuli to him, which the German king enfeoffed to his younger brother Duke
Henry I of Bavaria as the Imperial
March of Verona. When Otto had to deal with the revolt of his son, Duke
Liudolf of Swabia in 953, Berengar attacked the Veronese march and also laid siege to Count Adalbert Atto's
Canossa Castle. ==Losing control and death (961–66)==