 After renouncing his payments of tribute to the Fatimid caliphs, he sent an expedition to Sicily, but was forced by defeats on land and sea to evacuate the island completely.In 967, he made peace with the Fatimids and turned to defend himself against their common enemy, Otto I, who had proclaimed himself Roman Emperor and had attacked Byzantine possessions in Italy.After Al-Mustansir Billah, his sons Nizar and Al-Musta'li both claimed the right to rule, leading to a split into the Nizari and Musta'li factions respectively.