Siege of Constantinople (674–678)

Lore & Background

The siege followed years of Arab raids into Asia Minor and naval expansion under Mu'awiya, who became caliph in 661 after the First Muslim Civil War. In 672–673, Arab fleets secured bases along the coasts of Asia Minor, including Smyrna and Cyzicus, and established a loose blockade around Constantinople. Each spring from 674 to 678, the Arab fleet crossed the Sea of Marmara to assault the city's fortifications, withdrawing to Cyzicus for the winter. The Byzantines, under Emperor Constantine IV, used a new incendiary weapon—Greek fire—to destroy the Arab navy, while land forces defeated the Arab army in Asia Minor, forcing the siege to be lifted. A peace treaty followed, and the Byzantine Empire experienced a brief period of ascendancy after the outbreak of another Muslim civil war. The siege left traces in Muslim legends, often conflated with an earlier expedition in 669 led by Mu'awiya's son Yazid. Modern scholars James Howard-Johnston (2010) and Marek Jankowiak have questioned the accuracy of Theophanes's account, drawing different conclusions from Arabic and Syriac sources. News of the siege and peace treaty reached China and was recorded in Tang dynasty histories.

Reader's Guide

The Siege of Constantinople (674–678) was a pivotal event in early medieval history, representing the first major check to Arab expansion after decades of rapid conquest. The Byzantine victory, achieved through the innovative use of Greek fire and effective defense, temporarily stabilized the Byzantine Empire and halted Umayyad ambitions to capture the capital. The siege demonstrated the strategic importance of naval power and siege warfare, and its outcome influenced the balance of power between the Caliphate and Byzantium for decades. The event also highlights historiographical challenges: while Theophanes the Confessor provides the most detailed account, modern scholars have questioned its reliability, noting that Arabic and Syriac sources offer different perspectives on the siege's dating and even its existence. This uncertainty underscores the complexity of reconstructing early medieval history from fragmentary and sometimes contradictory records. The siege's legacy includes its incorporation into Muslim legendary traditions and its recording in distant Tang China, reflecting the wide-ranging impact of Arab–Byzantine conflicts.

Did You Know?

• The Byzantine victory was achieved using Greek fire, a liquid incendiary substance deployed from siphon-bearing ships.
• The Arab fleet used the peninsula of Cyzicus as a winter base, returning each spring to attack Constantinople.
• Modern scholars James Howard-Johnston and Marek Jankowiak have questioned the veracity of Theophanes's account of the siege.
• News of the siege and subsequent peace treaty reached China and was recorded in Tang dynasty histories.

The Umayyad Buildup and Strategic Ambition

Following the catastrophic loss at Yarmuk in 636, the Byzantine Empire withdrew its remaining forces behind the Taurus Mountains into Asia Minor, leaving Syria and Egypt to fall to the Rashidun Caliphate. From the 640s, Muslim raiders probed the Cilician frontier and pushed deep into Anatolia. Under Mu'awiya, then governor of the Levant, a naval force was deliberately cultivated; within a few years it was strong enough to seize Cyprus and raid as far as Kos, Rhodes, and Crete. The Battle of the Masts in 655 cemented Muslim naval supremacy. The First Muslim Civil War and the assassination of Caliph Uthman paused hostilities, and in 659 Mu'awiya even agreed to pay tribute to Constantinople. Once the Umayyads consolidated power in 661, however, aggression resumed. Muslim armies began overwintering on Byzantine soil west of the Taurus, strangling the imperial economy, while naval raids harried the southern Anatolian coast. The 669 expedition, which pushed as far as Chalcedon on the Asian shore of the Bosporus, demonstrated to Mu'awiya that a direct strike on the capital was conceivable—and that a permanent supply base in the region was essential to make it succeed.

The Phased Siege and the Weapon That Saved a City

The 674–678 siege was not a single desperate assault but a carefully sequenced operation. In 672 and 673, three major Muslim fleets were dispatched to secure sea lanes and establish coastal strongpoints between Syria and the Aegean. One fleet wintered at Smyrna, while others took positions along the Marmara and Aegean shores. The peninsula of Cyzicus, on the southern coast of the Sea of Marmara, was selected as the principal staging ground. From there, Arab forces spent each winter and returned every spring to press attacks against Constantinople's fortifications, tightening a loose blockade that aimed to sever the capital from the agricultural hinterland feeding it. The Byzantine response, under Emperor Constantine IV, came in two decisive blows. At sea, the Byzantine fleet deployed a revolutionary liquid incendiary weapon—Greek fire—annihilating the Arab navy and breaking the maritime component of the siege. On land, Byzantine forces routed the Arab army operating in Asia Minor. With both prongs of the siege shattered, the Arabs were forced to lift their grip on the capital.

Aftermath and the Shifting Balance of Power

The Byzantine victory in 678 was arguably the first significant Arab defeat in roughly fifty years of unbroken expansion. Its consequences rippled across the eastern Mediterranean. A peace treaty was concluded shortly after the siege ended, formalizing the new equilibrium. The respite proved longer than either side might have expected: the outbreak of a second Muslim civil war diverted Umayyad attention inward, and the Byzantines exploited the disruption to enjoy a brief period of strategic ascendancy over the Caliphate. For the Byzantine state itself, the survival of Constantinople meant the survival of the empire. Decades of territorial losses, economic strain from overwintering Arab armies, and the psychological blow of repeated defeats had left the state weakened but not yet broken. The repulsion of the siege temporarily stabilized the empire and preserved the political and cultural center of the Eastern Roman world. The Arab threat did not vanish permanently, but the 674–678 campaign marked a turning point in which the momentum of conquest, which had carried Muslim armies from the Levant to the gates of the capital, was finally checked by a combination of naval innovation and land-based resistance.

Memory, Myth, and the Question of What Really Happened

The siege of 674–678 left deep imprints on the collective memory of the nascent Muslim world, though those imprints are tangled with accounts of the earlier 669 expedition led by Mu'awiya's son Yazid. Arab chroniclers appear to have upgraded the 669 attack on Chalcedon—a suburb across the Bosporus—into a full assault on Constantinople itself, likely because Yazid's presence and the proximity of the two events made conflation natural. This blending of two separate campaigns has complicated modern scholarship. In 2010, Oxford historian James Howard-Johnston challenged the reliability of the Byzantine chronicler Theophanes the Confessor, whose account forms the backbone of the traditional narrative. More recently, Marek Jankowiak has pursued similar questions, drawing on Arabic and Syriac sources to reach conclusions that differ from Theophanes on both the dating and even the existence of a unified 674–678 siege. The event's reach extended far beyond the Mediterranean: news of the large-scale siege and the subsequent peace treaty traveled as far as China, where it was recorded in later Tang dynasty histories, testifying to the global significance of this confrontation.