Read this: The final son of Abd al-Malik to become caliph was Hisham (724–43), whose long and eventful reign was above all marked by the curtailment of military expansion. Hisham established his court at Resafa in northern Syria, which was closer to the Byzantine border than Damascus, and resumed hostilities against the Byzantines, which had lapsed following the failure of the last siege of Constantinople. The new campaigns resulted in a number of successful raids into Anatolia, but also in a major defeat (the Battle of Akroinon), and did not lead to any significant territorial expansion.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): Who stopped hostilities against the Byzantines?
unanswerable