Within two years of the consecration of the Cassinese Basilica, Alexander II died and was succeeded by Hildebrand as Pope Gregory VII. Desiderius was able to call forth the help of the Normans of southern Italy repeatedly in favour of the Holy See. Already in 1059 he had persuaded Robert Guiscard and Richard of Capua to become vassals of St. Peter for their newly conquered territories: now Gregory VII immediately after his election sent for him to give an account of the state of Norman Italy and entrusted him with the negotiation of an interview with Robert Guiscard on 2 August 1073, at Benevento. In 1074 and 1075 he acted as intermediary, probably as Gregory's agent, between the Norman princes themselves, and even when the latter were at open war with the pope, they still maintained the best relations with Monte Cassino. At the end of 1080 Desiderius obtained Norman troops for Gregory. In 1082 he visited the Italian king and future Holy Roman Emperor Henry IV at Albano, while the troops of the Imperialist antipope were harassing the pope from Tivoli. In 1083 the peace-loving abbot joined Hugh of Cluny in an attempt to reconcile pope and emperor, and his proceedings seem to have aroused some suspicion in Gregory's entourage. In 1084, when Rome was in Henry's hands and the pope besieged in Castel Sant'Angelo, Desiderius announced the approach of Guiscard's army to both emperor and pope.