The Syrian campaigns of John Tzimiskes were a series of campaigns undertaken by the Byzantine emperor John I Tzimiskes against the Fatimid Caliphate in the Levant and against the Abbasid Caliphate in Syria. Following the weakening and collapse of the Hamdanid Dynasty of Aleppo, much of the Near East lay open to Byzantium, and, following the assassination of Nikephoros II Phokas, the new emperor, John I Tzimiskes, was quick to engage the newly successful Fatimid Dynasty over control of the near east and its important cities, namely Antioch, Aleppo, and Caesarea. He also engaged the Hamdanid Emir of Mosul, who was de iure under the suzerainty of the Abbasid Caliph in Baghdad and his Buyid overlords, over control of parts of Upper Mesopotamia (Jazira).