Given the importance of the holy land to the Christians, as well as the importance of many great cities (Alexandria, Damascus and Jerusalem) to the Byzantine empire, why were not there any early attempts to recapture those strategic and religiosuly important land from the Arabs (either by the Byzantines or Rome)? Were the Byzantines so exhausted from their wars with the Sassanids that they relinquished these lands to the Arabs?
Well, one possible answer to this question may be rooted in the Slavic settlements within Greece proper, as well as Slavic settlements closely approaching Constantinople during the time when the Arab Muslims were conquering the Middle East-(such as Israel/Palestine & Egypt).
Although the Byzantines were engaged in constant conflict with the Persian Sassanian Empire to their East, the unanticipated Slavic settlements to their North, were a growing problem facing the Hellenic homeland, including, Constantinople. The Slavs never officially conquered or captured Constantinople, though they did manage to settle in sizable numbers throughout the Hellenic interior, as well as the wider Southern Balkan interior-(which, at time, was under Byzantine rule).
The Slavic settlements into mainland Greece-(and the Southern Balkans) during the Early Middle Ages, may have been a major geopolitical distraction for the Byzantine Empire and in turn, may have indirectly prevented the Byzantines from recapturing the Middle East from the Arab Islamic colonial onslaught. It appears from the historical literature of the Early Middle Ages that the Slavic settlements into Greece-(and the Southern Balkans) were initially, a major concern for the Byzantines and preserving their Middle Eastern sphere of influence was becoming less significant-(comparatively speaking).
Perhaps if the Slavs had not invaded mainland Greece, as well as the Southern Balkans during the Middle Ages, the Byzantines may have been able to have withstood the Arab Muslim campaigns into the Middle East......though of course it is pure speculation and theorizing.