Crusading Armies: How Medieval Campaigns Were Raised, Commanded, and Sustained

Crusading armies were forces assembled for particular campaigns, not branches of a single permanent military organization. The movement began with Pope Urban II’s call in 1095 and encompassed wars in the eastern Mediterranean as well as campaigns in Iberia, the Baltic, and within Europe. Crusading initiatives continued beyond the main medieval campaigns. Their armies varied with their purpose, location, and period, but commonly depended on a mix of personal commitments, noble leadership, foot soldiers, mounted fighters, and political cooperation.

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Recruitment began with a vow

Preaching invited people to take the cross: to make a religious vow to join a campaign. Church authorities promised spiritual benefits, including remission of sins, and could also protect the property and debts of those who went. These commitments helped draw participants, but did not turn them into a centrally enrolled force. A knight might travel as part of a lord’s retinue, meaning the group of followers attached to that leader, rather than finance and organize an expedition alone.

The costs could be substantial. One estimate for a knight’s participation in the First Crusade put it at the equivalent of four years’ income. Loans and gifts helped meet such expenses, while later campaigns also drew on church taxes and donations. In 1215, the Fourth Lateran Council allowed people unable to travel to fund a warrior’s journey in return for the full crusade indulgence; other donors could receive a partial one. A crusading host therefore included people who went to fight and, increasingly, people who supported a campaign financially.

Recruitment did not always produce the kind of force church leaders wanted. Urban II sought trained warriors, but popular enthusiasm helped send less organized groups ahead of the main First Crusade. These early contingents included many people without the resources or military experience of the later noble-led armies. Seljuk forces destroyed the group that reached Asia Minor in 1096. The early forces suffered from poor supply and coordination before the main noble-led armies reached Constantinople.

Infantry, cavalry, and the people who travelled with them

In Levantine campaigns, mounted knights formed an important striking force. They rode in armour, commonly used lances and swords, and could deliver a powerful charge when conditions allowed. Mounted squires and lighter-armed horsemen known as turcopoles also appear in accounts of crusader forces. Knights, however, were only one part of an army. Foot soldiers, usually more numerous, included men armed with spears, bows or crossbows. A crossbow held its drawn bowstring on a wooden stock until the trigger released a short projectile, allowing the weapon to be aimed while cocked.

Infantry and cavalry depended on one another. Foot soldiers could provide missile fire and support, while a disciplined body of infantry helped protect the mounted force from harassment. In some battle arrangements, archers opened the fighting as cavalry waited for a suitable moment to charge. The precise formation depended on the enemy and terrain. Against mobile horse archers, for example, a force needed to keep together rather than let individual groups be drawn away.

Campaigns also tested the relationship between a knight and his horse. Long marches, shortages of food and water, and lack of fodder could deprive mounted fighters of their animals. Knights might then fight on foot. An army’s numbers included more than its combatants, too: camp followers and other noncombatants travelled with some expeditions and also needed provisions. Estimates for the First Crusade’s main host at Constantinople range from 60,000 to 100,000 people, including about 30,000 noncombatants and up to 7,000 knights. These figures are estimates, not a precise muster.

Command was shared and often contested

The pope could authorize a crusade, promote recruitment, and appoint representatives, but the army in the field was usually led by nobles or rulers who brought their own followers. Contingents could retain separate leaders and priorities. A shared religious purpose did not guarantee a single chain of command, and disagreements over the route, target, or leadership could weaken a campaign.

The Fifth Crusade illustrates the problem. At Damietta, the crusaders chose John of Brienne as commander, but the papal legate Pelagius soon challenged his authority. Their disagreement took place within a shifting coalition of western and local forces. In other campaigns, a ruler’s presence could give an expedition greater political weight: no crowned king joined the First Crusade, while later expeditions included kings and emperors. Even then, high rank did not remove the need to negotiate with other leaders.

Allies and arrivals reshaped the host

Crusading forces operated among established states and communities, not in an empty landscape. Byzantine Emperor Alexios I Komnenos sought western military assistance, but required crusader leaders to swear that former Byzantine lands they recovered would be returned to him. Byzantine and crusader forces cooperated in the capture of Nicaea in 1097, even as mistrust and clashes complicated their relationship. In the north, Baldwin of Boulogne gained Armenian support before taking Edessa.

Local political interests could also create temporary partnerships across religious lines. Muslim rulers in Syria sometimes cooperated with Frankish leaders against regional rivals, while other local rulers offered terms such as safe passage. These arrangements depended on changing circumstances; they did not amount to a single, lasting alliance. Maritime powers such as Genoa, Pisa, and Venice also supplied ships or naval assistance to campaigns, often in return for commercial privileges.

An expedition’s force changed as it travelled. New contingents might arrive, while illness, battle, desertion, and the end of an individual’s vow reduced its numbers. After Jerusalem fell in 1099, most of the First Crusade’s participants returned west. Godfrey of Bouillon remained with a much smaller force, reported as 300 knights and 2,000 foot soldiers. The Fifth Crusade’s army at Damietta likewise grew and shrank as contingents arrived or departed. A campaign army was therefore a changing coalition, not a fixed establishment.

Paying for, moving, and supplying an expedition

There was no single source of money for every crusade. Participants and their patrons used personal wealth, loans, and gifts; popes and rulers also raised money through levies. To fund the Third Crusade, England and France imposed a tax known as the Saladin tithe, set at ten percent of income and movable property. Such measures could help assemble a force, but they did not guarantee that the planned number of people, ships, or supplies would be available.

The Fourth Crusade shows how transport agreements could shape a campaign. Venice agreed to provide a fleet intended for 33,500 crusaders, but only about a third of the expected force gathered there. The crusaders could not meet the agreed payment, and the resulting problem contributed to the expedition’s diversion from its original plan to attack Egypt. Transport was not simply a matter of getting soldiers to the coast: it connected recruitment, agreements with maritime powers, and the campaign’s political decisions.

Food, water, and fodder were equally important. Long overland routes could expose armies to shortages and attack. Sea travel could carry troops and supplies, and on the Third Crusade it helped limit the number of noncombatants travelling with the main force. For Louis IX’s expedition to Egypt in 1248, food and wine were stockpiled in Cyprus, with much of it brought from Apulia. The arrangements for each campaign depended on its route and destination; shortages could leave an army unable to continue even when its fighters remained in the field.

Sieges required time, equipment, and supplies

A field army could not take a walled city by cavalry charge alone. A blockade might last for months while besiegers tried to prevent defenders from obtaining food or water. An assault could require equipment and skilled labour, as well as the continued supply of the troops operating it. These demands made siege warfare closely dependent on transport and provisioning.

At Jerusalem in 1099, the crusaders’ siege stalled until Genoese craftsmen arrived with supplies. Their siege towers enabled an assault that helped the attackers take the city. A different danger arose in the field: at Hattin in 1187, the Jerusalemite army had been exhausted by a long march when Saladin’s forces defeated it. Together, these campaigns show that the outcome depended not only on weapons or courage, but on whether an army could reach its objective and remain effective there.

Campaign armies were distinct from military orders

Military orders maintained vowed communities and estate income between expeditions. Their brothers could garrison castles and join a campaign alongside temporary crusaders, hired troops and a ruler’s vassals. When visiting contingents returned home, an order’s local force and property administration continued, providing one element of the region’s longer-term defence.