War at Sea in the Middle Ages

By Andrew Latham and Rand Lee Brown II

“What, indeed, is more merciless than a naval battle, where men perish in water and flame!” – Flavius Vegetius Renatus, De Re Militari, 5th Century AD

That maritime warfare has been poorly covered in the literature on medieval warfare is beyond doubt. Similarly, there is little question that the medieval era has been inadequately addressed in the literature on naval warfare. In this series of articles, we will nevertheless attempt to bring the phenomenon of medieval maritime warfare to light, drawing on the relatively sparse literature that does exist to paint a picture of naval warfighting during the period from the fall of the Western Roman Empire in AD 476 to the onset of the Protestant Reformation in 1513. In so doing, we will not only investigate the changing character of medieval maritime warfare, but also explore some of the more consequential naval engagements of that era. A secondary goal will be to highlight some of the more recent historical discoveries that have expanded, challenged and even overturned many of longstanding assumptions regarding war at seas in the Middle Ages.


At the end of the old Roman world order, both the art and science of naval warfare was in a state of general neglect. After achieving a brutal and total victory over her only real maritime rival of Carthage in the Punic Wars and turning the Mediterranean Sea into a Roman lake, Rome’s naval activity was almost entirely confined to logistical army movements and the protection of sea trade from occasional piracy. Except for a few notable battles during various civil conflicts, the Imperial Navy had very little to show for itself by the time the Western Empire ceased to exist. This created a terrifying power vacuum in the Mediterranean waters that many attempted to fill, with varying degrees of success.

The sack of Thessalonica by the Arabs under Leo of Tripoli in 904, as depicted in the Madrid Skylitzes manuscript.

During the reign of Justinian I (527-565), the surviving Eastern Roman Empire reorganized itself into a potent maritime power whose navy made itself felt again all across the Mediterranean. However, they were not without rivals – first from barbarian hordes that had established virtual pirate states in formerly Roman Spain and North Africa, then from the even more formidable Arab states established after the rise of Islam in the 7th Century. Incessant civil conflicts and wars with its increasingly hostile neighbors meant that Byzantine naval superiority was spotty at best and, by the dawn of the High Medieval period, the Mediterranean once again played host to a broad number of contenders.


Sea power, as understood in the modern sense by anyone familiar with the term’s originator and High Prophet of naval war theory, Alfred Thayer Mahan, is a concept that revolves around two key points. First, there is the physical command of the seas through naval superiority (to be achieved through a decisive battle) and, second, the combined elements of naval power: commerce, overseas possessions, and access to foreign markets.

This definition was as true for the heads of medieval states as it is for heads of state today. The medieval world possessed an intense demand for goods trafficked across the various seas and rivers of their world – especially those states that almost exclusively relied on mercantile activity for their very existence, like the Italian city-state republics. However, the way that medieval rulers achieved sea power was decidedly different from the way it was achieved in Classical times or the way it is achieved in our own. Unlike these later periods, very few medieval states possessed standing navies of warships solely dedicated to maritime military activity.

Trade and food procurement were far higher priorities and, for much of the medieval period, the vast majority of ships and craft then were built for those purposes primarily, only engaging in warfare on a case-by-case basis when commandeered by a king or noble when required. The few proper warships we know of were normally small, sleek galleys that were almost exclusively confined to the Mediterranean and could only put out to sea for very short periods of time due to the logistical constraints imposed by the need to sustain large crews and the relatively small stowage space allocated to meet that need.

Additionally, naval warfare during this period involved very little actual ship-on-ship combat. The transportation of armies – like William of Normandy’s forces in 1066 or those crusader hosts that did not make their way to the Levant via the Byzantine lands – was a far more common activity for medieval military ships. As on land, sea combat normally took the form of commerce raiding and guerre de course rather than actual fleet engagements. Pitched battles, in general, were often seen as prohibitively risky by medieval commanders and naval warfare especially so. Those engagements that did take place were almost always fought within sight of land and focused more on boarding and capturing enemy craft as opposed to sinking them – a tactic imposed on commanders by the lack of any weaponry that could inflict enough damage to actually sink a ship.


Navigational capabilities were also extremely limited during this era, meaning that medieval seamen rarely ventured far out into open waters. This made deep-sea patrols and fleet interception virtually unthinkable. However, ship-on-ship combat did indeed occur in the medieval world – some of which left not only a lasting impact on the history of their time, but on our own as well. In our next few articles, we will examine some of the more significant – or at least interesting – of these engagements, focusing on how they were fought and why they were significant for their times and beyond.

Dr. Andrew Latham is a professor of political science at Macalester College in Saint Paul, Minnesota. He is the author, most recently, of a monograph entitled Medieval Sovereignty, to be published in 2020 by ARC Humanities Press.  You can visit Andrew’s website at or follow Andrew on Twitter @aalatham

Capt Rand Lee Brown II is a commissioned officer in the United States Marine Corps currently assigned to Marine Forces Reserve.  Holding a Master of Arts degree in Military History from Norwich University with a focus on medieval warfare, Capt Brown has written on military history for a variety of forums, including the Marine Corps Gazette and


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Further Reading:

Mahan, Alfred Thayer. Mahan on Naval Warfare ( Dover Publications, 2011)

Stanton, Charles D. Medieval Maritime Warfare (Pen & Sword Books, 2015)

Top Image: Bibliothèque nationale de France MS Français 50, fol. 149v.