The conquest of Central Asia by Muslim Arabs, which was completed in the 8th century AD, brought to the region a new religion that continues to be dominant. The Arabs first invaded Mawarannahr in the middle of the 7th century through sporadic raids during their conquest of Persia. Available sources on the Arab conquest suggest that the Soghdians and other Iranian peoples of Central Asia were unable to defend their land against the Arabs because of internal divisions and the lack of strong indigenous leadership. The Arabs, on the other hand, were led by a brilliant general, Qutaybah ibn Muslim, and were also highly motivated by the desire to spread their new faith (the official beginning of which was in AD 622). Because of these factors, the population of Mawarannahr was easily subdued. The new religion brought by the Arabs spread gradually into the region. The native religious identities, which in some respects were already being displaced by Persian influences before the Arabs arrived, were further displaced in the ensuing centuries. Nevertheless, the destiny of Central Asia as an Islamic region was firmly established by the Arab victory over the Chinese armies in 750 in a battle at the Talas River.