 Complete the following phrase:  In 654, the city was captured for the first time by the Arabs of the Rashidun Caliphate, under Muawiyah, the future founder of the Umayyad Caliphate. At about the same time, the themes were established in Anatolia, and Ancyra became capital of the Opsician Theme, which was the largest and most important theme until it was split up under Emperor Constantine V r. 741775; Ancyra then became the capital of the new Bucellarian Theme. The city was captured at least temporarily by the Umayyad prince Maslama ibn Hisham in 73940, the last of the Umayyads territorial gains from the Byzantine Empire. Ancyra was attacked without success by Abbasid forces in 776 and in 79899. In 805, Emperor Nikephoros I r. 802811 strengthened its fortifications, a fact which probably saved it from sack during the large-scale invasion of Anatolia by Caliph Harun al-Rashid in the next year. Arab sources report that Harun and his successor al-Mamun r. 813833 took the city, but this information is later invention. In 838, however, during the 