 Umayr's subsequent campaign against the large Christian Banu Taghlib tribe in the Jazira sparked a series of tit-for-tat raids and further deepened Arab tribal divisions, the previously neutral Taghlib throwing in its lot with the Yaman and the Umayyads.The Taghlib killed Umayr in 689 and delivered his head to Abd al-Malik.Along Syria's northern frontier, the Byzantines had been on the offensive since the failure of the First Arab Siege of Constantinople in 678.