The adoption of iconoclasm seemed indeed to be vindicated in the Emperor's eyes, for success returned to the Imperial arms, and the Muslims suffered a series of defeats between 727 and 732. The next years were more difficult, especially as the Arabs defeated the Khazars and forced their leader to convert to Islam. In 740 however the emperor and his son scored a decisive victory over an invading Arab army at Akroinon, which halted the momentum of the Arab attacks.