1. The elements of historical geography

Control of the Black Sea was the Byzantine Empire’s constant aim throughout its history. The main purpose was to discourage foreign powers from settling there and threatening Constantinople itself, the privileged position of which offered the ability to control access to and from the Black Sea, by controlling the adjacent regions’ entrepôt trade.

The empire’s immediate sphere of influence in the Black Sea included its western coast as far as the mouth of the Danube, the Crimea and Asia Minor. The region of modern Ukraine was also important for Byzantium, because of the navigable rivers emptying into the Black Sea between the Danube and the Caucasus, opening ways for Byzantine trade reaching as far as central and northern Europe and Scandinavia. As regards the Crimea, only its southern and southeastern parts were Byzantine territory, because their lands were fertile, they were and of great commercial and strategic importance in relation to Russia, and presented defensive advantages.¹ The Black Sea was indispensable in meeting the Byzantine capital’s demanding need for grain supplies, particularly after the Arabs conquered Egypt.² Furthermore, naphtha (a petroleum byproduct), the main ingredient of Byzantium’s “secret weapon”, Greek fire, oozed from natural springs mainly in the region between the Caspian and Black Seas.³

2. The Early Byzantine period

Already from the time of Constantine the Great (324-337) the greater part of the Black Sea hinterland had slipped from the empire’s control: the northern rivers, the mountain passes in the Caucasus, even the Danube plain, abandoned by Rome in the third century.⁴ The raids of the Goths in the second half of the third century had further weakened Rome’s hold of the region, while a century later the Huns crushed (ca. 370) the Ostrogoths (who had conquered the area north of the Black Sea) and founded an empire that stretched from the Caspian Sea to the Rhine.⁵ Justinian I (527-565) succeeded in establishing Byzantine authority over a large part of the Black Sea, having secured, among other things, a Persian resignation (treaty of 561) from any claim to Lazica, on the eastern corner of the Black Sea,⁶ which thus became a Byzantine lake for the most part. Indeed, in order to secure control over the regions of the Caucasus and the Crimea, also claimed by the Persians, in the sixth century Byzantium had instigated a grandiose missionary scheme among the people of the those regions (Abasgians, Alans, Goths, Laz etc.).⁷ Procopius describes in the Buildings Justinian’s building activity as regards fortifications on the shores of the Black Sea, aiming at strengthening Byzantine positions. The construction of an aqueduct in Trebizond is noteworthy, while the repair of the city walls of Cimmerian Bosporus and Cherson in the Crimea was significant.⁸

3. Byzantine policy in the Black sea during the seventh - tenth c.

The second half of the seventh century saw the foundation of the Khazar state, which until its destruction in the tenth century by the Kievan Rus’ (Russians) will expand from the Black to the Caspian Sea and from the Caucasus to the western bank of the Lower Volga. Although other people (Bulgarians, Pechenegs) claimed parts of the Black Sea area, the Khazars became the strongest power in the region,⁹ where they came into the focus of Byzantine diplomacy.

In ca. 626 Heraclius (610-641) made an alliance with the Khazars¹⁰ and succeeded in crushing Persian forces in the southern Caucasus, paving the way for an invasion to the Persian state itself. Later the Khazars proved valuable allies against the Arabs as well, but there were also moments of tension between them and the Byzantines, mainly due to clashes over the eastern Crimea.¹¹

The primary objective of Byzantine foreign policy in the Black Sea, particularly its northern part, was the preservation of the integrity of the frontier in the Danube and the Haemus mountain range, against an endless series of raids conducted by “barbarian” nations. Particularly in the seventh - tenth centuries, these nations included Bulgarians, Avars, Khazars, Magyars, Pechenegs, and Rus’. Byzantine foreign policy, therefore, was of a defensive character, while the consequences of its failures were particularly poignant.¹²

In order to implement its policy in the northern Black Sea, Byzantium relied on maintaining control over Cherson and other regions along the southeastern coast of the Crimea,¹³ from which it kept an eye on developments and moves by potential enemies in the steppe of south Russia. Therefore, the Crimea was the key in a Byzantine early-warning system on the empire’s northern frontier. However, for the system to function uninterrupted, two problems had to be faced: Cherson’s tendency to be autonomous from Constantinople; and the wish of neighboring states or people (Khazars, Magyars, Pechenegs, and Rus’) to appropriate Byzantine Crimea.¹⁴

Regarding the second problem, when Byzantium itself was unable to intervene militarily, Byzantine diplomacy attempted to provide a solution, by the notorious tactic of “divide and rule”, playing off one people against the other, through gifts and monetary subsidies.¹⁵ Should that method fail, imperial policy possessed other “weapons”, the most important of which was religion, since the Byzantines were convinced that Christianizing the barbarians brought them within the empire’s sphere of influence and made them more amenable to negotiations. Thus the Bulgarians were converted to Christianity in the ninth century, while an attempt to Christianize the Khazars in the same century met with failure.¹⁶

The Rus’ had launched a number of attacks against Constantinople, sailing across the Black Sea (beginning in 860). The Byzantines were quick to realize that the Rus’ could be useful commercial partners and allies, against whom they could use the neighboring Pechenegs whenever they judged that the Rus’ had to be contained.¹⁷ In 988 Vladimir (972-1015), ruler of Kiev, became a Christian, and his baptism open the way for Byzantine cultural influences that would shape the civilization of medieval Russia.¹⁸

4. Byzantium’s gradual loss of control over the Black Sea (eleventh - fifteenth c.)

Although the Black Sea littoral of Asia Minor had been Byzantine for centuries, the arrival of the nomadic Türkmen would gradually alter the situation in the greater Asia Minor area in favor of the Turks. The Seljuk Turks’ victory against the Byzantines in Mantzikert, Armenia, in 1071 open the way for a large-scale Türkmen migration as far as the Aegean.¹⁹ In the following centuries, control over a large part of Asia Minor would gradually pass in the hands of various local Turkish emirs coming from the Türkmen hordes. The arrival of the Mongols in the thirteenth century resulted in an even greater immigration of Türkmen nomads, ending in a new nexus of emirates, the authority of which reached the Black Sea coast. In fact, in 1215/6 the Seljuks succeeded in establishing a permanent naval base at Sinope.²⁰

The Byzantines, however, were not to lose control of the Black Sea to one of the aforementioned opponents, but to the Westerners. The Fourth Crusade led to the fall of Constantinople (1204) and the partition of the Byzantine Empire among Crusaders and Venetians. Greek successor states emerged in former Byzantine territories, the strongest being the empire of Nicaea in western Asia Minor. In 1204, however, the empire of Trebizond was also founded, by the brothers Alexios (the First [1204-1222]) and David Komnenos, grandsons of emperor Andronikos I Komnenos (1183-1185).²¹ The southeastern coast of the Black Sea remained under the authority of Trebizond until 1460,²² while the important city of Cherson accepted Trebizond’s suzerainty from the first years of the empire’s foundation.²³

During the reign of the Komnenoi (1081-1185) and their successors, the Italian maritime cities of Venice, Genoa and Pisa had received numerous commercial privileges in Byzantine territory. However, up to and including the twelfth century, Byzantium seems to have maintained a trade monopoly in the Black Sea and did not allow foreign merchants to travel there.²⁴ But in 1261, with the treaty of Nymphaion, signed in return for assistance offered by their fleet against the Venetians in the imminent recapture of Constantinople, Michael VIII Palaiologos (1259-1282) gave the Genoese numerous customs exemptions and trading bases. Thus Genoa cemented its power in the Levant. It slowly dominated trade in the Black Sea, where the Genoese colony of Caffa (Theodosia) in the Crimea was the centre of a profitable economic region.²⁵ The Byzantines had forever lost the profits from this trade, but by now the time of the Ottomans had come: in 1453 Constantinople was conquered, in 1461 Trebizond was taken and in 1475 the whole of the Crimean peninsula fell into their hands.²⁶