site.btaTervel of Bulgaria and the 717 Siege of Constantinople

On August 15, 718, the Arab army besieging Constantinople suffered a crushing defeat by the Bulgar forces of Khan Tervel of Bulgaria. As a result, the Arab siege was lifted. Historians, researching these events from today’s perspective, sum up that "By turning back the Moslem invasion, Europe remained in Christian hands, and no serious Moslem threat to Europe existed until the fifteenth century. This victory, coincident with the Frankish victory at Tours (732), limited Islam's western expansion to the southern Mediterranean world." (Paul K. Davis)

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Modern historians still argue on details, numbers and reasons left by chroniclers of Byzantine, Arab and Western origin, but the general picture justifies a conclusion about decisive set of events with far reaching implications.

During the summer of 717 the Arabs crossed the Dardanelles and besieged Constantinople with an army of some 200,000 men and 2,500 ships. The second Arab siege of Constantinople was far more dangerous for Byzantium than the first (674-678), as the Arabs launched a direct attack on the Byzantine capital and attempted to cut off the city completely from land and sea. Their leader, Maslama ibn Abd al-Malik, accepted the unique challenge: to besiege the then largest city of the world known for its superb fortifications. Maslama, Caliph Sulaiman’s own brother, was a talented and experienced commander, having already fought with the Byzantines and the Khazars.

Faced with this serious threat, the newly crowned Emperor Leo III made a plea to Bulgarian ruler Tervel for help. The Emperor relied on a treaty concluded a year earlier. Tervel agreed, and his troops fought the Arabs more than once during the siege.

Maslama persisted with the siege despite the hard winter with more than three months of snowfall. The vague and sometimes conflicting details talk about the victorious Byzantine navy and heavy clashes on land. It is known that the Arabs built two trenches around their camp – one facing the Bulgarian army and the other - the walls of the city. A bloody battle marked the end of the siege. According to Theophanes, the Bulgars killed some 22,000 Arabs in the battle. Sigisbert van Gembloers suggests that the number is closer to 30,000. Shortly after, the Arabs raised the siege.

From a military point of view, the role of Tervel’s army in defeating the Arabs during the siege was crucial. Tervel’s forces had blocked Maslama’s army on land for months – a strategy that led to disastrous results for the invaders, such as famine and diseases. Such a task could not be completed without cavalry superiority – and Tervel was opposed by the famous Rashidun cavalry the Arabs formed during their conquests in the second half of the 7th century.

Historians disagree on various details, one reason being the later Muslim and Christian sources that added fictional details and legendary elements. History, however, agrees on the importance of the battle with its wide-ranging repercussions for the development of the region.

These events weakened the Umayyad state and changed the balance in the region. Arab sources claim that altogether 150,000 Muslims perished during the campaign. Modern historians are accustomed to usage of improbable numbers of men and soldiers in ancient sources, but, as Byzantinist John Haldon puts it, the figure, "while certainly inflated, is nevertheless indicative of the enormity of the disaster in medieval eyes".

The rescue of Constantinople ensured the survival of Byzantium, while the Caliphate leaders abandoned the goal of outright conquest. This postponed the Muslim advance into South-East Europe for several centuries. Military historians often include the siege as of the decisive battles of world history.

Tervel’s role won him recognition and respect – both needed by the Bulgarian state, which had only been established north of the Balkan ridge a few decades earlier - in 681.