 During the 9th century , Byzantium had gradually recovered its strength and internal stability while the Caliphate had become increasingly impotent and fractured . Under Kourkouas 's leadership , the Byzantine armies advanced deep into Muslim territory for the first time in almost 200 years , expanding the imperial border . The emirates of Melitene and Qaliqala were conquered , extending Byzantine control to the upper Euphrates and over western Armenia . The remaining Iberian and Armenian princes became Byzantine vassals . Kourkouas also played a role in the defeat of a major Rus ' raid in 941 and recovered the Mandylion of Edessa , an important and holy relic believed to depict the face of Jesus Christ . He was dismissed in 944 as a result of the machinations of Romanos Lekapenos 's sons but restored to favour by Emperor Constantine VII ( r . 913 – 959 ) , serving as imperial ambassador in 946 . His subsequent fate is unknown . 
