The period the dynasty of Isaurians reigned can be characterized as the most critical one as regards relations between the Arabs and the Byzantines. Leo III, the first representative of the dynasty, when he ascended to the imperial throne, in 717, had to cope with a large-scale Arab assault against Constantinople.
The Arab general Maslama in the summer of 717 blockaded the Basileuousa (appellation of Constantinople meaning "regnant") by land and sea. However, the competence of the emperor, the epidemics that hit the Arabic camp and the wide use of "Greek fire" on the part of the Byzantines were the basic factors that contributed to the final defeat and retirement of the Arabic land forces a year later (718) as well as to the destruction of their fleet.
The victory of the Byzantines against Arabs in 717 was of primary importance, since this prevented their penetration into Europe from the South-east. Of equal importance was the victory of Charles Martel against Arabs at Poitiers in France, in 732, which also averted Arabic expansion into Europe. The following Isaurian emperors, despite the internal disorders caused to the state due to the iconoclastic movement and the other external enemies they had to confront, marked also several successes against the Arabs. Both Constantine V and his successor Leo IV won important victories. Not until the years of the last representatives of the dynasty, of Constantine VI and Irene, did the Arabs manage, after a series of successive raids into Asia Minor to return after having accorded favourable peace conditions (783).