Miniature depicting the Byzantine Navy repelling the Russians during the siege of Constantinople in 941

The Byzantine Navy: From maritime dominance to decline

The Byzantine navy was vital to the empire’s defense and dominance, securing trade routes and repelling invasions with innovations like Greek Fire. Though initially a maritime superpower, it gradually declined due to economic challenges and reliance on foreign fleets.

The Navy in the early Byzantine time: the golden time.

In the 6th century, Byzantine warships established control over the seas by recapturing Carthage and destroying the Vandal fleet. During this period, the navy primarily functioned as a police force operating from Constantinople and various Mediterranean bases. However, in the mid-7th century, the emergence of Slavic pirates and the development of Arab naval power under Mu’awiya necessitated a major naval reorganization. The fleet of the Karabisianoi was created to defend the Byzantine coastline and the approaches to Constantinople.

Following the dissolution of the Karabisianoi under Leo III, regional fleets were established, financed independently through the naval strateia. These fleets were organized within the exclusively maritime themes of the Kibyrrhaiotai (by 732), Aegean Sea (by 843), and Samos (by 899). The imperial fleet (basilikon ploimon), based in Constantinople and commanded by the droungarios tou ploimou, was responsible for protecting the capital and undertaking expeditions, often with contributions of ships and manpower from the thematic fleets. The navy achieved its greatest successes in the 10th century, notably with the destruction of the Rus’ fleet in 941, the reconquest of Crete in 961, and Cyprus in 965.

Miniature of the Skylitzes manuscript showing the use of the Greek Fire by the Byzantine navy

The Greek Fire, an incendiary weapon said to have been invented by Kallinikos to defend Constantinople from the Arabs in 678, was a redoutable weapon to strenghten the naval power. The mixture, probably of crude oil with resine and sulfur, was heated and projected via a pump (siphon) through a bronze tube (strepton). The liquid jet was ignited either as it exited the tube or by flaming projectiles fired after it. Frequently used during naval battles, but also in the land military, it ensured a tactical advantage and proved redoutably efficient, for instance in the siege of Constantinople by the Arabs in 678 or by the Rus´ in 941. The secret of the composition and operation was a closely guarded secret which got lost after the Fourth Crusade.

Revival and Collapse: The Middle Byzantine Navy under the Komnenoi.

While the Byzantine navy saw a decline in the 11th century, particularly with the collapse of the thematic fleet system and the increasing reliance on foreign maritime powers, it would be inaccurate to characterize the entire Middle Byzantine period as one of simple naval decay. Instead, the navy underwent a structural transformation, especially under the Komnenian emperors, who recognized the strategic necessity of maritime strength in the face of rising threats from the Normans, Seljuks, and Italian city-states.

Under Alexios I Komnenos (1081–1118), the navy was initially weak and heavily reliant on Venetian aid. In exchange for naval support against the Normans, Alexios granted Venice generous trade privileges, which would later prove economically damaging. Despite this, Alexios took steps to revive a native fleet, laying the groundwork for later developments.

A true naval resurgence occurred under Manuel I Komnenos (1143–1180). He invested heavily in rebuilding the fleet, not only expanding its size but also improving ship construction and recruitment. Manuel’s navy undertook several bold expeditions, the most notable being the capture of Damietta in Egypt in 1169, conducted jointly with the Crusader Kingdom of Jerusalem. Though ultimately abandoned due to logistical issues and political disagreements, the campaign demonstrated the renewed operational reach and ambition of the Byzantine navy.

Manuel also waged naval campaigns in the Adriatic, challenging Norman and Venetian dominance. He established a strong Byzantine presence in the region and constructed naval bases to support fleet operations. Moreover, he sought to counterbalance Italian maritime influence by playing Genoa, Pisa, and Venice against each other in a complex web of diplomacy and military pressure.

However, the gains of the Komnenian period were not sustained after Manuel’s death. His successors lacked his strategic vision and failed to maintain the fleet. As the 12th century drew to a close, Byzantium became increasingly dependent on Italian mercantile fleets, especially the Venetians and Genoese, who would eventually dominate Byzantine commerce and even politics. By the time of the Fourth Crusade, the empire’s naval power was a shadow of what it had been under Manuel I. This weakening proved catastrophic when in 1204, Venetian ships breached the sea walls of Constantinople, enabling the Crusaders to sack the city. The fall of the capital – largely due to Byzantium’s inability to defend its coastline and harbors- marked a profound rupture in imperial history and exposed the consequences of naval neglect.

Reduced naval ambitions in the Late Byzantine times.

Byzantine navy, light galley depicted on an icon in the Byzantine Museum in Athens
A light galley depicted on a 14th century icon

The decline of the Byzantine navy at the end of the 12th century was not reversed by the Nicaean Empire. While the navy remained active and occasionally successful, reliance on Italian naval power through alliances and diplomacy continued, as exemplified by the Treaty of Nymphaion in 1261. This agreement between Michael VIII Palaiologos and the Republic of Genoa provided Genoese naval support in exchange for commercial privileges. Although it facilitated the recapture of Constantinople that same year, the long-term effects of such policies were detrimental, undermining both Byzantine maritime independence and economic stability.

While Michael VIII Palaiologos had the last significant Byzantine fleet built, it was disbanded by his successor Andronikos II Palaiologos. Later, Andronikos III’s small navy, under the command of the megas doux Alexios Apokaukos, achieved some success against the Genoese.

John VI Kantakouzenos also constructed a small flotilla, but by the end of the 14th century, Byzantium naval power was insignificant and the control of the seas had firmly passed to the Italians and the Turks. In 1453, a small and outdated Byzantine fleet defended the Golden Horn but was outmaneuvered when Mehmed II brought Ottoman ships overland into the harbor. Though the final assault to Constantinople came by land, Ottoman naval control isolated the city and ensured its fall.

References

  • H. Ahrweiler, Byzance et la mer (Paris, 1966).
  • L. Bréhier, “La marine de Byzance du VIIIe au XIe siècle,” Byzantion 19 (1949), 1-16.
  • F. H. van Doorninck, “Byzantium, Mistress of the Sea: 330-641,” in A History of Seafaring, ed. G. F. Bass (New York-London, 1972), 133-158.
  • E. Malamut, “Les insulaires des Xe-XIIe siècles: marins ou soldats?” JOB 32