Castles throughout the Middle Ages went through immense evolution, especially their defensive structures. This is because the defensive capabilities of the castle were its main reason for existing, and the castle needed to keep up with siege-craft technology which was evolving just as rapidly throughout the medieval period. In Late Antiquity, the Romans were masters of building defensive structures within several days while on campaign in Gaul and the British Isles. Such structures included walled barracks for the armies to sleep in and watchtowers known as burgus for defending roads and bridges, precursors to the Scottish pele which encompassed the border ‘twixt Scotland and England during the time of Robert the Bruce.

While Western Rome was declining during the Migration Period of the Early Middle Ages, many of the forts and stone walls the Romans had built in Europe remained intact, and most of them were repurposed by Celtic and Germanic peoples. Even some famous medieval cities originally grew up within Roman walls. One of these palimpsests is York. In finite terms, these early defensive structures in Europe were a result of foreign invaders traveling into new lands and wishing to keep their conquered possessions secure by having safe bases of operation where soldiers could quickly respond to uprisings and enemy campaigns. Moreover, Julius Caesar became famous for his use of contravallations and circumvallations when besieging a fortress in Gaul, which not only kept his besiegers safe from sorties but safe from outside relief forces as well, preventing all egression in or out of the beleaguered stronghold.

As the Early Middle Ages neared closer to the High Middle Ages, Celtic and Germanic peoples began to experiment further with their own defensive structure designs, and as one traveled through the European landscape they would see many of what we call motte and bailey castles. These were primarily constructed out of wood and so very few are still extant, but the mottes they were built on, earthworks resembling would-be burial mounds for giants, can still be seen from the sky today alongside the fosses that surround them. Motte and bailey castles, much like the later stone castles we will soon discuss, were typically multifunctional, allowing the lord who sometimes took residence in the keep and his serfs and bondsmen who lived in and around the bailey, not to mention the cottars who lived in the immediate area, security from banditry and competing strongmen. Also, guests traveling from afar, if the lord of the estate knew them or indeed if the traveler was willing to pay a fee, could be welcomed inside for hospitality as a hôte.

These wooden splendors of architecture, however, would peter out of use as the technology of warfare marched onward. Governance in the High Middle Ages became more competent and organized, which meant armies, with their commissariats and battering-trains, became larger. Siege-works such as the trebuchet and battering ram operated by these larger armies rendered motte and bailey castles rudimentary and new innovations in defensive design were needed. This is when we start to see the classic stone castle we love so much in Disney movies and Game of Thrones, especially as William the Norman brought his architects with him to the British Isles, transforming the Anglo-Saxon landscape with Frankish castles for his vassals. In Late Antiquity and much of the Early Middle Ages, stone castles of this sort, with their counter-embattled ramparts and donjons that speared the firmament, had never existed before, although Africa and Asia since ancient times had sported many stone fortresses of similar design. Stone castles of the High Middle Ages were a direct result of private warfare among European barons and especially large-scale military campaigns waged ‘twixt puissant princes, kings, emperors, archbishops and popes. Good examples of these are the crusader castles in the Holy Land or the English castles in Wales.

In their early stages, these behemoths of rock stacked on rock had, alongside the iconic crenel and merlon, relatively thin walls, simple gates and one or two baileys. By the Late Middle Ages, however, the walls of these structures grew thicker, their gates became more complex with the additions of the gatehouse and murder hole, and, most importantly, they could now have three or more baileys, making the job of reaching the keep, the castle’s last stronghold in the innermost bailey, an arduous task requiring much determination on the besiegers’ part. The revival of ancient tactics of mining under walls to collapse them and building earthen ramps to circumvent them also brought on the addition of more turrets, bastions, machicolations and, perhaps most importantly, barbicans to defend the drawbridge as well as wider moats often flooded with water if a lake or river was close enough. A trebuchet could still pose a great threat to structures such as these, but it was the job of the defenders to counterpose a sally on horseback to prevent the trestles of trebuchets from being erected by the besiegers in the first place. More so than the earlier motte and bailey castle and much like the Roman burgus, these later masterpieces of stone were built around strategic geographical locations like crossroads, mountain peaks, bridges, et cetera, and their primary purpose was to keep these strategic locations and the lands around them in desirable hands.

In the latter half of the fifteenth century, these castles evolved dramatically again as the cannon, or crackys of war and pot-de-fer as other cultures called them, a siege machine which had been used sparingly since the fourteenth century, became more prevalent in medieval warfare. A device known as a petard, too, if placed on a gate, postern or vulnerable section of wall could blow a hole wide enough for a storming party to breach a castle. This caused walls to become even thicker and gatehouses to become more effective. Also, other new defensive structures such as the batter and redan for deflecting cannon shot were introduced. The overall geometry of castles shifted, too, as boomers, masons and architects realized the conventional rounded towers and circular curtain-walls which had been so formidable against trebuchets in the High Middle Ages were now a weakness against the more lethal cannon shot of the time, and so star-shaped castles began to appear with the advent of trace italienne design. Later in the early modern period and the Great War of the twentieth century, these castles, which by now should be called super fortresses, would evolve again to withstand perpetual artillery either by land or, more interestingly, by sea as ordnance by this time was a necessity on any warship. Overall, however, by the seventeenth century, the castle would never be the medieval marvel we iconize today. Today, we can travel through Europe and visit the ruins of these marvelous structures, but their uses in the world, besides as residences for people whom I am jealous of, are no longer needed. Therefore, this discussion will end with a vehement exclamation: long live the medieval castle!

Sources of Information and Further Reading:

Caesar, Julius, and Cornelius Marshal Lowe. Caesar’s Gallic War. Scott, Foresman, 1907.

Gies, Joseph, and Frances Gies. Life in a Medieval Castle. Barker, 1974.

Parker, Geoffrey. The Military Revolution: Military Innovation and the Rise of the West, 1500-1800. Cambridge University Press, 1996.