Arab–Byzantine wars

The Battle of Mu'tah was one of the earliest direct military engagements between the forces of the First Islamic State and the Byzantine Empire, placing it at the opening of the long Arab–Byzantine confrontation that would define much of the following four centuries. Fought near the village of Mu'tah in Palaestina Salutaris east of the Jordan River, the battle set Muslim forces against a Byzantine army reinforced by Ghassanid vassals. The disparity in recorded force sizes — 3,000 for the Islamic State against 10,000 for the Byzantine and Ghassanid side — indicates the scale of the challenge faced by the Muslim expedition. Three successive commanders on the Islamic side were engaged during the fighting, with Khalid ibn al-Walid assuming command in the course of the battle. The engagement established an early precedent for direct Islamic military contact with Byzantine frontier forces and their Arab client states, foreshadowing the far larger campaigns that would follow under the Rashidun Caliphate in the following decade.

The Muslim conquest of the Levant, conducted by the Rashidun Caliphate between 634 and 638 CE, transferred Byzantine Syria from Roman imperial control to Arab Muslim governance, constituting one of the most consequential territorial shifts of the Arab–Byzantine wars. The campaign was directed at the highest levels of the Rashidun state, with Caliph Abu Bakr and his successor Umar ibn al-Khattab overseeing operations carried out by a command structure that included Khalid ibn al-Walid, Abu Ubayda ibn al-Jarrah, Amr ibn al-As, and Yazid ibn Abi Sufyan, among others. The Byzantine defense was led by Emperor Heraclius alongside commanders including Vahan and Theodore Trithyrius, as well as the Ghassanid client ruler Jabalah ibn al-Aiham. The loss of Syria permanently removed a core Byzantine province from imperial control and established the Rashidun Caliphate as the dominant power across the Levant, setting the geographic and political framework within which the Arab–Byzantine wars would continue for centuries.

The Rashidun Caliphate's conquest of Byzantine Egypt, carried out by forces under Amr ibn al-As between 639 and 642, represented one of the most consequential territorial transfers of the Arab–Byzantine wars. The campaign ended Roman rule over Egypt, a dominion that had persisted since 30 BC — a span of roughly seven centuries — and more broadly brought to a close the Greco-Roman period of Egyptian history, which had endured for close to a millennium. The loss of Egypt struck at a core Byzantine province: economically productive, strategically positioned, and deeply embedded in the administrative and ecclesiastical structures of the empire. For the Rashidun Caliphate, the acquisition extended Arab power across North Africa and delivered resources and population that would underpin further expansion westward along the Mediterranean littoral.

The Muslim conquest of the Maghreb, commencing in 647 and concluding in 709, resulted in the Rashidun and Umayyad Caliphates seizing the entirety of the Byzantine Exarchate of North Africa, with the Byzantine Empire losing its final strongholds in the region to Caliph al-Walid I at the campaign's close. The conquest forms a component of both the broader Arab–Byzantine wars and the wider century of rapid early Muslim expansion. The campaigns required successive commanders — including Amr ibn al-As, Uqba ibn Nafi, Hassan ibn al-Nu'man, and Musa ibn Nusayr — to overcome Byzantine resistance led by figures including Gregory the Patrician, Kusaila, and Dihya across more than six decades of intermittent warfare. The elimination of Byzantine authority in North Africa removed a strategically significant imperial presence from the southern Mediterranean littoral and established Caliphate control over territory that would serve as the staging ground for subsequent operations, including the crossing into Iberia under Tariq ibn Ziyad.

The Battle of the Masts, fought in 655, was a naval engagement between the Rashidun Caliphate and the Byzantine Empire in which the caliphate's forces were commanded by Abu al-A'war and the Byzantine side was led directly by Emperor Constans II. The battle is notable as an early major naval confrontation within the Arab–Byzantine wars, a conflict spanning over four centuries. Beyond identifying the principal commanders on each side, the available record does not preserve force sizes, casualties, a precise location, or a confirmed outcome.

The Umayyad siege of Constantinople, launched under Mu'awiya ibn Abi Sufyan, represented one of the most ambitious military undertakings of the Arab–Byzantine wars. Constantinople's position at the junction of Europe and Asia, where the Bosphorus connects the Sea of Marmara to the Black Sea, made it the preeminent strategic objective in the broader contest between the Umayyad Caliphate and the Byzantine Empire. As a transcontinental city astride the Silk Road, its capture would have severed Byzantine control over a nexus of commercial and military movement between two continents. The engagement resulted in substantial losses on both sides — 25,000 Umayyad and 17,000 Byzantine casualties recorded — indicating the intensity and duration of the effort. The city held under Constantine IV, preserving Byzantine authority over the crossing between Europe and Asia and denying the Caliphate a foothold that would have fundamentally altered the balance of the Arab–Byzantine conflict.

The Battle of Sebastopolis, fought in 692 CE at Sebastopolis in the Armeniac Theme, marked the formal rupture of the peace that had existed between the Byzantine Empire and the Umayyad Caliphate since 680. That truce had held for over a decade, representing a period of relative stabilization in the protracted Arab–Byzantine conflict. The engagement at Sebastopolis, commanded on the Umayyad side by Muhammad ibn Marwan and opposed by the Byzantine commanders Leontius and Neboulos, brought this interval to a close and resumed active hostilities between the two powers. Its primary significance within the wider Arab–Byzantine wars lies in this role as a turning point: the battle ended a negotiated pause and reactivated the contest over the frontier zones of Anatolia and Armenia that had defined the conflict across much of the seventh century.

The Umayyad siege of Constantinople in 717 was among the most ambitious military undertakings of the Arab–Byzantine wars, deploying a reported 120,000 troops against a Byzantine garrison of 15,000 in an attempt to take the city that served as the intersection of Europe and Asia along the Bosporus, connecting the Sea of Marmara and the Black Sea. Constantinople's position on the Silk Road gave it exceptional strategic value, and its capture would have represented a transformative blow to Byzantine power and a gateway for Umayyad expansion into Europe. The Umayyad Caliphate committed forces under Maslama ibn Abd al-Malik, with backing from the caliphs Sulayman ibn Abd al-Malik and later Umar ibn Abd al-Aziz, alongside commanders including Umar ibn Hubayra and Abdallah al-Battal. The Byzantine defense was organized under Leo III the Isaurian, with support from the Bulgarian ruler Tervel. The campaign ended at enormous cost to the Umayyad side, with recorded losses of 150,000, exceeding the entire initial force — a figure that points to catastrophic attrition over the course of the siege. The failure to take Constantinople preserved Byzantine control of the Bosporus corridor and checked Umayyad expansion westward, marking one of the most consequential repulses of the Arab–Byzantine conflict.

The Battle of Akroinon was fought in Phrygia, on the western edge of the Anatolian plateau, between a large Umayyad Arab force and a Byzantine army commanded by Emperor Leo III and his son, the future Constantine V. The 740 expedition was the largest Arab incursion into Anatolia in recent decades, organized in three separate divisions; one of those divisions, numbering 20,000 men under Abdallah al-Battal and al-Malik ibn Shu'aib, was met and decisively defeated by the Byzantine forces. Umayyad casualties reached 13,200, a loss representing the bulk of that division. The defeat at Akroinon, combined with the Umayyad Caliphate's concurrent difficulties on other fronts and the internal instability surrounding the Abbasid Revolt, effectively ended major Arab raiding into Anatolia for three decades. The battle thus marked a turning point in a cycle of Arab incursions that had persisted for nearly a century, relieving sustained pressure on the Anatolian interior at a moment when Umayyad power was entering a period of structural crisis.

The Battle of Anzen (Dazimon) on 22 July 838 was fought in the context of a large-scale Abbasid retaliatory expedition launched in response to Byzantine emperor Theophilos's military successes the previous year. The Abbasid campaign was organized as two separate armies with the strategic objective of sacking Amorion, one of Byzantium's largest cities. Theophilos moved to confront one of those armies — the smaller force commanded by the Iranian vassal prince Afshin — at Dazimon, while the broader Abbasid operation continued to target the Byzantine heartland. The battle thus forms a critical episode within the wider Abbasid offensive of 838, which culminated in the assault on Amorion and represented one of the most significant Arab military thrusts into Byzantine Anatolia during the long Arab–Byzantine conflict.

The Abbasid siege and sack of Amorium in August 838 was one of the most consequential Abbasid military successes of the Arab–Byzantine Wars. Caliph al-Mu'tasim selected Amorium deliberately: it was the birthplace of the reigning Byzantine dynasty and one of the largest and most important cities in Byzantine Asia Minor, making its fall a direct symbolic and material blow to imperial prestige. The campaign was itself a retaliatory response to a Byzantine expedition into Abbasid borderlands the previous year, and al-Mu'tasim prosecuted it at the head of a force roughly twice the size of what Theophilos could field. The defeat of the Byzantine emperor at Anzen allowed Abbasid columns to penetrate deep into Asia Minor, take Ancyra unopposed, and converge on Amorium — a sequence that exposed the limits of Byzantine defensive capacity in the east. Byzantine casualties recorded between 30,000 and 70,000 underline the scale of the disaster. Theophilos was unable to relieve the city due to the rebellion of his Khurramite contingent and political intrigues at Constantinople, compounding the military failure with a demonstration of internal instability. The fall of the dynasty's home city carried lasting resonance within the long conflict between the Abbasid Caliphate and Byzantium.

The Battle of Lalakaon, fought in 863 in Paphlagonia, was a significant engagement in the long-running Arab–Byzantine wars. The confrontation pitted a Byzantine force under Petronas, uncle of Emperor Michael III, against an Arab army led by Umar al-Aqta, the emir of Melitene. Arab sources also place the Emperor himself on the field. The battle marked a major Byzantine effort to repel an Arab incursion into Paphlagonia, a region in northern Anatolia, reflecting the ongoing contest for control over the Anatolian frontier that defined much of this centuries-long conflict between the Byzantine Empire and the Abbasid Caliphate and its associated frontier emirate forces.

The sack of Thessalonica in 904, carried out under the command of Leo of Tripoli on behalf of the Abbasid Caliphate, resulted in recorded Byzantine casualties of 5,000. Thessalonica was the second city of the Byzantine Empire, and its sack represented one of the most damaging Arab naval operations of the prolonged Arab–Byzantine conflict. The attack demonstrated the continued capacity of Abbasid-aligned forces to strike deep into Byzantine-held territory in the Aegean despite ongoing Byzantine naval and land resistance across the wider frontier.