Castle construction was an important force multiplier in medieval warfare, where a small well-provisioned garrison behind well-constructed walls could hold out against a numerically larger siege force for weeks or even months until a relieving army arrived or the siege broke due to aggravating factors like battlefield attrition, disease, or the end of annual feudal obligations or campaigning contracts. During Europe’s Age of Crusades in the Latin East (1099-1291 CE) urban fortifications, existing castle improvements and new castle construction became essential elements to the new Catholic occupiers’ strategy to first secure and then expand their foothold in the Levant during the First (1096-1099) and Second Crusades (1147-1149), and hold on to imperiled possessions after the successful Muslim counter crusade by Salah al-Din ibn Ayyub (Saladin in the West, r.1174-1193), and the contraction of Latin holdings from the Third Crusade (1189-1192) forward until the end of the crusading era in the Levant, usually dated with the fall of the Crusader stronghold at Acre in 1291. 

Right:  Krak des Chevaliers (completed in 1170) was built on a hilltop over 2,100ft above the west bank of the Orontes valley floor, surrounded by moderately steep slopes to discourage sieges. It served as headquarters to the Hospitallers in Syria. This type of castle building was brought back to Europe by returning crusaders, influencing castle building in the twelfth and thirteenth centuries. Similar castle complexes were built in Spain and the Baltic by crusader forces. Damaged in the recent Syrian civil war, it is a UNESCO World Heritage Site. Source: Wikimedia. Click to enlarge.

The crusaders faced numerous impressive urban fortifications during their expedition across to Anatolia toward Syria in the first phase of the First Crusade. In 1097 a crusader host, assisted by Byzantine troops sent by Emperor Alexios I Komnenos (r.1081-1118), sieged the strategically important city of Nicaea, then in the hands of the Seljuk Turks, famous for its impressive three miles of curtain walls averaging thirty-three feet in height and over a hundred bastions for flanking fire along the wall’s length. After a thirty-six day siege, the city gave itself up to the Byzantines accompanying the Catholic crusaders, restoring the city to Byzantium but denying the city to a crusader storm and pillage. Nicaea’s defense gave the crusaders an example of the importance of a strong fortification in a hostile land. Later, after reaching Syria, the crusaders faced the walls of Antioch and its Turkish defenders. Built during the reign of Justinian (r.527-565), Antioch’s massive circuit walls were nearly three miles in length, up to thirty-three feet in height and punctuated by over sixty towers, some as tall as sixty-five feet in height and most within supporting bowshot of one another.  The northern wall was a double wall. Six main gates and numerous smaller gates punctuated the walls, allowing defenders to sally forth and harass the crusaders. Using the mountainous terrain surrounding the city itself to best effect, Antioch’s citadel was located along the southeast section of the walls in a commanding position near the 1,000-foot high Mount Silpius. The crusaders eventually prevailed after an eight month siege (October 1097-June 1098), only to turn around and defend the city from a Turkish relief army, now relying on the city’s impressive fortifications for their own defense. After scattering the besieging force in a brilliant but risky offensive sortie, the crusaders shored up their defenses at Antioch, making it an important lynchpin in the crusader grand strategy. Antioch would remain an important regional capital and crusader state, lasting until Mamluk siege breached the walls and took the city in 1268. With their lines of communication secure, the crusaders continued south the Syrian and Palestinian coast, reducing wall cities along the way until they finally reached the Holy City of Jerusalem and its battlements and towers.

Jerusalem was encircled by nearly two-and-half miles of walls averaging nearly forty feet in height and eight feet in thickness. The walls contained five main gates and dozens of watch towers (the current walls surrounding Old Jerusalem date to the Ottoman period and have seven main gates and thirty-four towers). However, the city was devastated by an earthquake in 1033, and laid in ruins until the Fatimids took the city in 1098, afterwards repairing the city’s fortifications with rubble from damaged churches but reducing the size of the walled enclosure (the old Jewish Quarter south of the Temple Mount was left outside of the repaired walls, with the Jewish population given new accommodations in the northeast corner of the city). Even with shorter walls, the size of Jerusalem’s fortifications made a full-scale siege impossible, so the crusaders attacked the northwestern corner of the city, finally gaining entry after a thirty-eight day siege and proclaiming the Holy City the new capital of Catholic fiefdoms on the Levantine coast of West Asia.  

The first Catholic ruler in the Holy Land to understand the importance of strong fortifications to the crusading effort was Baldwin I (r.1100-1118), a veteran of the sieges of Nicaea, Antioch, and Jerusalem. As the newly crowned king of the Latin Kingdom of Jerusalem, Baldwin ruled directly over the largest of what would become four individual crusader states, the First Latin Kingdom of Jerusalem (1099-1187), joining the County of Edessa (1098-1150), the Principality of Antioch (1099-1268), and the County of Tripoli (1104-1289). Collectively, these new Catholic possessions in the eastern Mediterranean were referred to as Outremer, French for the land “overseas.” To defend the newly created crusader states, Baldwin ordered the reinforcement of existing urban fortifications and the construction of new crusader castles in strategically important locations across the Levant. Jerusalem’s walls were reinforced, with a double-wall defensive system built in the vulnerable northeastern corner of the city, the location of the crusader’s successful storm in 1099. The city’s citadel, the Tower of David, was repaired and would be expanded in the 1170s with the construction of additional towers and its own curtain walls to form a fortified enclosure. 

Right: Chastel Blanc was one of the earliest major crusader castles constructed by the Latin occupiers in the twelfth century. Bult in a manner similar to the great rectangular keeps in Catholic Western Europe (London’s White Tower, Rochester Castle, Trim Castle). Chastel Blanc proved too vulnerable to siege die to its square construction and lack of layered concentric curtain walls, with Catholic military engineers later favoring the castle-complex as the premier castle design in the Levant. Source: Wikimedia. Click to enlarge.

Strengthening port fortifications in Palestine, Lebanon, and Syria was also a crusader priority. Ports serving the kingdom of Jerusalem included Beirut, Sidon, Acre, Haifa, Caesarea, Arsuf, Jaffa, and after the successful Venetian Crusade of 1122-1124, Tyre. Along this coastline, existing landward walls were reinforced to withstand sieges, and new towers were added to man-made moles at the mouth of harbors, some with booms that could be raised or lowered to block the harbor’s entrance. In some places, anti-shipping siege engines were installed. Additionally, walls were often erected between the harbors and the city itself as an additional barrier in case an enemy navy seized the harbor. Similar port fortifications existed north in County of Tripoli and the Principality of Antioch. Inland, few crusader town were protected by circuit walls (Tiberias on the Sea of Galilee being a notable exception). Instead, the crusaders built numerous kinds of towers, castles and concentric castle complexes to protect the region.  

The simplest and most common form of crusader fortification was the free-standing tower often associated with a noble family. No more than fifty-feet in height and containing two stories, these simple towers were roofed with stone groin or barrel vaults. Most of these towers were isolated structures, while others were the strongest building arranged around a courtyard where defenders could take refuge in times of war. Medieval fortifications utilized towers of different shapes, depending on purpose, cost, and topography. Square towers were the easiest to construct and had the most usable interior room, but their corners were vulnerable to attack from sapping and, due to their flat surface, from projectile weapon. They also did not provide the best field of fire for defenders. Round towers (sometimes called drum towers) were more resistant to siege techniques (sapping and throwing weapons), and were stronger architecturally, but had less usable interior room. In fact, medieval military engineers experimented in polygonal towers, sometimes to meet the demands of topography and sometimes for aesthetic purposes (Theodosian Walls of Constantinople had polygonal towers). Most towers contained multiple floors that included food and water stores, armories, magazines (for throwing weapons and later cannons), and barracks, making towers self-sufficient during sieges in case they are cut off from the rest of the fortification. Towers could also be the location of private residences for prominent lords (the grandmaster’s quarters for the various monastic military orders was usually located in a strong tower). 

Warfare in the Age of Crusades: The Latin East. 344 pages, Hardcover. Pen & Sword Military, 2023. By Brian Todd Carey (Author).

From the publisher, "Warfare in the Age of Crusades: The Latin East explores in fascinating detail the key campaigns, battles and sieges that shaped the crusading period of the Middle Ages, giving special attention to military technologies, tactics and strategies. Key personalities and political factors are addressed, including the role of papal monarchy in initiating the crusading expeditions, the relationship between Catholic Europe and the Byzantine Empire, the role of the religious military orders, and Islamic and Mongol military capabilities. Chapters are devoted to each of the major crusades to the Levant – First, Second, Third and Fourth crusades – and an analysis of the Islamic response. The rise of the Mamluks in Egypt, with their innovative military organization, is covered, as are the failed Egyptian and Tunisian campaigns. The concluding chapters describe the Mongol campaigns in the Levant, the Mamluk response, and the final siege of Acre in 1291."

About the Author: Brian Todd Carey is an Assistant Professor of History and Military History at the American Public University System, where he teaches ancient, classical, medieval and early modern military history. He is the author of dozens of history articles in numerous magazines and journals, including Aviation History, Command Magazine, History Magazine, Marine Corps Gazette, Medieval History Magazine, Military Heritage, Military History, Strategy and Tactics, World History Bulletin, World at War, World War II, and WWII Quarterly: The Journal of the Second World War and seventeen articles on ancient, classical and medieval Eurasian warfare for the twenty-one volume ABC-CLIO-World History Encyclopedia. In 2007 he was the recipient of the American Public University System's Excellence in Teaching and Learning Award for the School of Arts and Humanities. He is the author of Warfare in the Ancient World, Warfare in the Medieval World, Hannibal's last Battle: Zama and the Fall of Carthage, and Road to Manzikert: Byzantine and Islamic Warfare, 527-1071.  ☞  Buy on Amazon

 The early crusaders also built larger rectangular keeps (sometimes referred to as Romanesque castles) enclosed by a stone wall. This type of fortification was common in western Europe by the end of the eleventh century and its most famous example is the Norman conqueror of England, William I’s (r.1066-1087) famous White Tower (completed in 1078 and today part of the Tower of London castle complex). In the Latin East, these rectangular keeps were two rather than three stories high but were still made of solid construction. One such structure was Chastel Blanc overlooking the town of Safita in northwestern Syria. Built in the mid-twelfth century and garrisoned by the Knights Templar, Chastel Blanc was 102 feet long, fifty-nine feet wide, and rose to the height of ninety-two feet, with ashlar walls nearly ten feet thick. Most medieval wall constructions used ashlar construction where available stones were cut into shapes with square edges (meaning stones of irregular size were pieced together like a large jigsaw puzzle to create the wall face). These irregular shaped stones were held in place with a mortar made from a mixture of water, sand, and lime. Two of these walls were built, one facing outward towards the attacker, and the other facing inward towards the bailey or city, with the space between the two walls filled with a rag stone rubble core.

Chastel Blanc, along with another smaller one anchoring the defense of the coastal city of Jebail (ancient Byblos on the Lebanese coast), proved too small to meet the manpower needs of the crusaders. They were also too expensive and took too long to construct. The solution was to build new fortifications based on Byzantine and Islamic designs already present in the Levant. These castle complexes did not rely on a massive rectangular keep, but instead imitated urban fortifications by enclosing a large space or bailey within curtain walls (sometimes double walls) with battlemented towers placed at intervals along its length, and powerful gatehouses protecting its entrances. Inside the walls the crusaders constructed barracks, magazines, stables, mess halls, kitchens, latrines, storehouses, and in the case of castles built to house members of the monastic military orders, chapels and chapter houses.

Right: Map of Crusader States in the Twelfth Century. Click to enlarge.

The most remarkable of these crusader castle complexes is Krak des Chevaliers. Built in the County of Tripoli in what is now western Syria near the border of Lebanon, the original fortress was built in the Byzantine era and used by successive Islamic powers until the crusader conquest. Given to the Knight Hospitallers in 1144 by Raymond II, count of Tripoli (1137-1152), the first Krak des Chevaliers was completed in 1170 as a standalone Romanesque castle and served as an administrative base for the monastic military order for another hundred years. Earthquakes would periodically damage the fortification, requiring renovation and expansions until a full concentric castle complex was created in the thirteenth century. Krak des Chevaliers was built on a hill-top over 2,100 feet above the west bank of the Orontes valley floor, surrounded by moderately steep slopes to discourage sieges. The outer defenses consisted of a polygonal wall that contained several defensive galleries and semicircular towers. Between the outer and inner defenses was a forecourt that contained the stables, magazine for siege engines, baths and latrines. It also contained a deep rock-hewn ditch that served as a water reservoir. The inner stronghold was built on a steep revetment and contained cisterns, storehouses, barracks, a cloister and a chapel. Entrance to the fortress was through three fortified gatehouses, each separated by narrow corridors within the range of fire of defending walls. This passageway made three ninety-degree turns before it reached the inner ward and allowed an armored knight to ride the entire distance from the main gate to the inner ward without dismounting. Five large towers protected the inner stronghold, each containing multiple floors that included food and water stores, armories, magazines, and barracks, making towers self-sufficient during sieges in case they were cut off from the rest of the fortification. One tower was reserved for the Grandmaster of the Knight Hospitaller, serving as his personal residence and administrative office. During a siege, each of these towers had enough provisions to hold out on their own for weeks. As a castle complex, Krak des Chevaliers could hold a garrison of over 2,000 soldiers and proved to be a resilient fortification. It withstood numerous sieges, including a prolonged siege by Saladin in 1188, and other Islamic attacks in 1207, 1218, 1229, 1252, 1267, and 1270 before finally taken in 1271 by the Bahri Mamluk Sultan Baybars (r.1260-1277) after an extensive six-week siege. The formidable defenses of Krak des Chevaliers and other crusader castle complexes would inspire European military engineers to construct similar fortifications in western Europe, most notably the Edwardian castles designed by Master James of Saint George (c.1230-1309) in northern Wales (Caernarfon Castle, Conwy Castle, Harlech Castle, Beaumaris Castle, Rhuddlan Castle, and Flint Castle). 

Crusader engineers built or renovated fortifications along all major trading routes across the region, with a special eye to using the terrain as a force multiplier whenever possible. Towers and castles were located on hills, in mountain passes, along rivers and lakes, and at the edge of deserts. Sometimes existing Byzantine or Islamic forts were restored, while other times new fortifications were built on the locations of old ones. Although some forts were placed on the border of the frontiers, the crusaders concentrated on a defense in depth strategy by building castles in the interior to serve as forward operating bases for garrisons besieging Muslim towns or to raid Muslim lands. These fortifications would later serve as refuges during Islamic raiding or invasions. Castle building in the crusading era left an indelible mark on the Levantine countryside, with many of these castles still visible to onlookers as either magnificent ruins or protected and occasionally restored monuments to Europe’s two hundred year occupation of Syria, Lebanon, and Palestine during the Age of Crusades.

Suggested Readings: 

Carey, Brian Todd, Joshua B. Allfree, and John Cairns. Warfare in the Age of Crusades: The Latin East. Pen and Sword, 2023.

DeVries, Kelly and Robert Douglas Smith. Medieval Military Technology, second edition. University of Toronto Press, 2012.

Kennedy, Hugh. Crusader Castles. Cambridge University Press, 2001.

Nicolle, David. Crusader Castles in the Holy Land, 1097-1192. Osprey, 2004.