Writing the history of a medieval battle is, in some ways, very different to writing about more recent conflicts. Obviously, there are no photos or film footage available; nor can you interview the participants. The same is true of Waterloo or Blenheim. But those campaigns produced mountains of written documents which allow us to recreate them in minute detail. These might be self-consciously ‘historical’ sources, written as a record of the battle (official histories, memoirs), or contemporary documents that tell us so much about the lived experience of war: correspondence, both private and official, shipping manifests, receipts, orders, records of the courts martial, muster rolls, sick lists, etc.

The medieval historian lacks most of these. Europe in the thirteenth century was still primarily an oral and visual culture. Literacy was a specialist skill. Mass produced paper was not available. Parchment (made from treated animal skins) was expensive and reserved for important or prestigious documents. Day-to-day working was done on slates with chalk or on offcuts of parchment that would be scraped clean, over and over, until they fell apart. The kind of documents that we might use to recreate a battle of the eighteenth or nineteenth century rarely survive from the thirteenth, if they ever existed in the first place.

This does not mean that we are wholly in the dark. One of the remarkable things about the battle of Bouvines is that a handful of critical documents have survived, allowing us to recreate the order of battle with a reasonable degree of accuracy. The reign of Philippe II of France (1165–1223) was marked by the expansion of royal bureaucracy, as the king and his ministers became increasingly involved in the daily government of the kingdom. The Servitia Feodorum of 1211–12 is a record of the soldiers that royal vassals (people who held land from the king) were obliged to send to the king’s army when called upon. This can be combined with other sources, including the Catalogus Captivorum, a document created shortly after Bouvines listing the noble prisoners taken by the French and which towns had responsibility for guarding them, to give us a reasonable idea of the barons, knights and urban communities that made up Philippe’s army on that campaign.

These documents tell us something about the armies involved but what about the battle itself? Medieval military historians rely heavily on contemporary narrative histories, known as chronicles, to learn how a particular battle was fought. The vast majority were written by churchmen who were neither soldiers nor present for the events they recorded. Even the most scrupulous author could only present a partial account of a battle, which means they must always be read with a critical eye. Another remarkable fact about Bouvines is that we possess an eyewitness’s account of the battle. King Philippe’s chaplain, Guillaume le Breton, wrote two accounts of his master’s reign: one in prose (the Gesta Philippi) and the other in verse (the Philippide). In the Gesta, he tells his readers that he stood behind the king’s position at Bouvines with the other clergy, singing psalms and praying for victory. Together, Guillaume’s two accounts allow us to recreate Bouvines at a level of detail that is simply not possible for many other medieval battles: who was positioned where, the sequence of manoeuvres that began the fighting and the conspicuous acts of valour (or cowardice) performed on that hot July afternoon.

Chronicles are the foundation for any medieval military history but they have their own limitations. For example, they contain very few details about arms and armour, either because the authors did not know them or because they assumed that their audience would already be familiar with such mundane objects and did not pay them much attention, expect when they had a direct impact on the narrative. Guillaume le Breton tells us almost nothing about the foot soldiers who made up the majority of both armies at Bouvines. We do know that some of the coalition’s foot soldiers were armed with ‘hooks and slender lances’ because, Guillaume wrote, they used them to pull King Philippe from his horse, threatening his life.

How, then, do historians find out about the gear used in a medieval battle? Archaeology is of limited help here: few military artefacts from the early thirteenth century have survived into the twenty-first century. The major sources for understanding the arms and armour of this period are works of art. Sculptures are very important, as one of the few three-dimensional representations of contemporary military gear. For example, William Longespée, Earl of Salisbury, who was captured fighting in the press at Bouvines, is depicted on his tomb effigy in Salisbury Cathedral in full knightly armour, including his heraldic shield: a vital source for how the aristocracy of this period might be equipped for battle.

Another medieval form of artwork with a surprising military dimension is the seal: a clay or metal stamp that was pressed into wax to authenticate documents. From the twelfth century onwards, it became fashionable for noblemen to depict themselves as mounted knights on their seals, giving us a chronological record of the changes in military equipment as each generation commissioned a new seal in the latest fashion. 
To these can be added images from illustrated, or ‘illuminated’, manuscripts. The most prestigious histories, Bibles and works of literature of the age were accompanied by illustrations depicting scenes from the narrative. Even when depicting the battles of the Old Testament or the Trojan War, medieval illustrators would invariably depict them in contemporary arms and armour. These are not photographs, nor are they technical drawings, but some are highly detailed and can be combined with other sources to learn more about weapons, armour and other everyday objects used in medieval warfare. Many illustrated manuscripts have been digitised and can be accessed for free online. The so-called ‘Crusader Bible’, commissioned for Philippe II’s grandson, Louis IX, is arguably the finest source for thirteenth-century arms and armour and can be viewed in its entirety on the Morgan Library’s website.

We do not have all the information we could want about medieval warfare (a common complaint from historians of all periods), whether this is because the evidence is lost or incomplete, or because there are cultural differences between their society and ours. But we can still learn a surprising amount. By drawing on a range of source materials, and employing a little reasoned guesswork, we can recreate the military experience of another time and place, an era both exotically different and compellingly familiar. The costumes, language and values may seem strange but, with a little effort, studying medieval battles can reveal a history with universal resonance: stories of courage, skill and camaraderie, of suffering, terror and cruelty, experiences and emotions common to the knights at Bouvines, the conscripts who marched behind Napoleon or the Tommies on the Western Front.

Find out more in Bouvines 1214: Philippe Augustus and the Battle for France