Al-Mu'tasim gained power in 833 and his rule marked the end of the strong caliphs. He strengthened his personal army with Turkish mercenaries and promptly restarted the war with the Byzantines. His military excursions were generally successful, culminating with a resounding victory in the Sack of Amorium. His attempt to seize Constantinople failed when his fleet was destroyed by a storm.^[38] The Byzantines restarted the fighting by sacking Damietta in Egypt. Al-Mutawakkil responded by sending his troops into Anatolia again, sacking and marauding until they were eventually annihilated in 863.^[39]