al-Qasim, who had declared a Holy War (jihad) against Otto, retreated when he noticed the unexpected strength of Otto II's troops when the latter was not far from Rossano Calabro. Informed of the Muslim retreat, Otto II left his wife Theophanu and young son Otto III (along with the Imperial treasury) in the city and marched his army to pursue the Muslim force. Unable to flee back to his stronghold in Sicily due to an Ottonian naval blockade, al-Qasim faced Otto's army in a pitched battle south of Crotone at Cape Colonna on July 14, 982. After a violent clash, a corps of Otto II's heavy cavalry destroyed the Muslim center and pushed towards al-Qasim's guards, with the Emir killed during the charge. Despite the Emir's death, the Muslim troops did not flee the battlefield but regrouped and managed to surround the Imperial soldiers, slaughtering many of them and inflicting a severe defeat upon the Emperor. According to the Muslim historian Ibn al-Athir, Imperial casualties numbered around 4,000. Landulf IV of Benevento and Pandulf II of Salerno, Bishop Henry I of Augsburg, Margrave Gunther of Merseburg, the Abbot of Fulda, and numerous other Imperial officials were among the battle's casualties. The Imperial defeat shocked the political makeup of Southern Italy. With two Lombard princes dead, the Principalities of Capua and the Benevento passed to younger branches of the Landulfid family. Though the Muslim troops were forced to retreat to Sicily after their victory, the Muslims remained a presence in southern Italy, harassing the Byzantines and Lombards. This Ottonian defeat, the worst in the history of the Empire at the time, greatly weakened Imperial power in southern Italy. The Byzantines joined forces with the Muslims and regained possession of Apulia from Ottonian forces. Imperial crisis Succession issues The defeat at Stilo forced Otto II to flee north to Rome. He then held an Imperial Diet at Verona on Pentecost 983. He sent his nephew Otto I, Duke of Swabia and Bavaria, back to Germany with news of the defeat and to call the German nobles to the assembly, but his emissary died en route on November 1, 982, in Lucca. News of the battle did cross the Alps, however, reaching as far as Wessex in England, signifying the magnitude of the defeat. Duke Bernard I of Saxony was heading south for the assembly when Danish Viking raids forced him to return