Isaurian Dynasty
The Byzantine Empire was ruled by the Isaurian or Syrian dynasty from 711 to 802. The Isaurian emperors were successful in defending and consolidating the Empire against the Caliphate after the onslaught of the early Muslim conquests, but were less successful in Europe, where they suffered setbacks against the Bulgars, had to give up the Exarchate of Ravenna, and lost influence over Italy and the Papacy to the growing power of the Franks.
The Isaurian dynasty is chiefly associated with Byzantine Iconoclasm, an attempt to restore divine favour by purifying the Christian faith from excessive adoration of icons, which resulted in considerable internal turmoil.
By the end of the Isaurian dynasty in 802, the Byzantines were continuing to fight the Arabs and the Bulgars for their very existence, with matters made more complicated with the resurrection of the Western Empire under Charlemagne.
Read more about Isaurian Dynasty: Background: Byzantium in The 7th Century, The Empire in Crisis, 705–717, Leo III The Isaurian, 717–741, Constantine V, 741–785, Leo IV, 785–790, Constantine VI and The Regency of Irene, 785–797, Irene's Sole Rule and Downfall, 797–802