In Arabia, Muhammad founded Islam in 632. His followers rapidly conquered territories in Syria and Egypt. They soon were a danger to the Byzantine Empire. In the 8th and 9th centuries, the Byzantine Empire stopped Islamic expansion and reconquered some lost territories. In 1000 A.D. the eastern Empire was at its height: Basileios II reconquered Bulgaria and Armenia. Culture and trade flourished. In 1071 the Battle of Manzikert led the empire into a dramatic decline. For the Byzantine Empire this meant centuries of civil wars and Turkic invasions. The Muslim caliphate had an Golden Age under the Abbasids.