Arab–Byzantine wars
The Arab–Byzantine wars were a series of wars from the 7th to 11th centuries between multiple Arab dynasties and the Byzantine Empire. The Muslim Arab Caliphates conquered large parts of the Christian Byzantine empire and unsuccessfully attacked the Byzantine capital of Constantinople. The frontier between the warring states remained almost static for three centuries of frequent warfare, before the Byzantines were able to recapture some of the lost territory.

The conflicts began during the early Muslim conquests under the expansionist Rashidun Caliphate, part of the initial spread of Islam. In the 630s, Rashidun forces from Arabia attacked and quickly overran Byzantium's southern provinces. Syria was captured in 639 and Egypt was conquered in 642. The Exarchate of Africa was gradually captured between 647 and 670. From the 650s onwards, Arab navies entered the Mediterranean Sea, which became a major battleground. Both sides launched raids and counter-raids against islands and coastal settlements. The Rashiduns were succeeded by the Umayyad Caliphate in 661, who over the next fifty years captured Byzantine Cyrenaica and launched repeated raids into Byzantine Asia Minor. Umayyad forces twice placed Constantinople under siege, in 674 to 678 and 717 to 718, but were unable to capture the heavily fortified Byzantine capital.

Following the failed second siege, the border stabilized at the Taurus Mountains in Asia Minor. The Umayyads launched frequent attacks across this frontier, which was heavily fortified by both sides and the surrounding region became depopulated. During this period, the Byzantines were usually on the defensive, avoiding open field battles and preferring to retreat to their fortified strongholds. After 740 they began to launch their own raids across the frontier and by sea.

In 750 the Umayyads were overthrown by the Abbasid Caliphate, who were less expansionist than their predecessors and did not seek to eliminate the Byzantines; embassies were exchanged and there were several periods of truce. Nevertheless conflict remained the norm, with almost annual raids and counter-raids, either by the Abbasid government or by local client rulers, which continued until the mid-10th century. Byzantine attempts to take back the lands they had lost only provoked Abbasid retaliation, in the form of destructive invasions of Asia Minor. Arab naval raids reached a peak in the 9th and early 10th centuries: their fleets attacked the coasts of Italy and Dalmatia, while Abassid vassals conquered Crete in 827 and gradually took Sicily from 831 to 878.

Due to political instability beginning in 861, the Abbasid state entered a period of decline and fragmentation. Simultaneously, the Byzantines began a resurgence under their emperors of the Macedonian dynasty. From c. 920 to 976, the Byzantines pushed Arab forces back, recovering some of their lost territories in northern Syria and Armenia. The Emirate of Crete was reconquered in 961. By the end of the 10th century the Fatimid Caliphate had replaced the Abassids as the major Arab power; they halted the Byzantine reconquests although border conflicts continued. The frontier remained stable until the Seljuk Turks began to take territory from both the Arabs and Byzantines in the 1040s and 1050s, forming the Seljuk Empire and beginning the Byzantine–Seljuk wars.
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