 Complete the following phrase:  Sources available on the historical personality of Abdallah al-Battal consist of legends often written in the mesnevi style, and which may comport historically correct elements or points that support each other, as well as contradictions. For example, he is cited as having participated in his twenties to the Second Arab Siege of Constantinople in 718, and the legends name his Byzantine enemy as Leon, which could be no other than Leo III the Isaurian, the Emperor during the siege. On the basis of this information, his date of birth is reckoned to be around 690-695 and there is a consensus among historians for accepting 740 as the year of his death, at the 