During the First Crusade, western European armies travelled from Europe to Constantinople, crossed Anatolia, defeated several Muslim forces, captured major cities including Nicaea and Antioch, and eventually conquered Jerusalem in 1099. The expedition began after Pope Urban II's appeal in 1095, with the main military contingents departing in 1096. Participants followed different routes and were led by several independent commanders rather than one supreme commander.
They had to negotiate with the Byzantine emperor Alexios I Komnenos and provide assurances concerning captured territories. The campaign was characterised by prolonged marches, severe shortages, disease, internal disagreements, major sieges and repeated battles. The capture of Jerusalem was the expedition's central military and religious objective and was followed by the establishment of Latin Christian political states. The campaign was therefore a long and difficult military movement rather than one continuous battle.
The early mobilisation produced the People's Crusade, which travelled ahead of the main aristocratic armies. Large groups of ordinary participants followed preachers and local leaders, but many lacked adequate military organisation, supplies and discipline. Some crusaders participated in attacks on Jewish communities in the Rhineland, producing massacres and forced conversions. These attacks were a major episode of religious violence associated with the mobilisation but were not part of the principal military campaign in the eastern Mediterranean.
The People's Crusade reached Anatolia and was confronted by Seljuk forces. In October 1096, a large section of the movement was defeated and destroyed near Civetot. Survivors returned to Constantinople or joined later forces. The failure demonstrated the difference between popular enthusiasm and the logistical and military organisation required for a major expedition across thousands of kilometres.
The main crusader armies reached Constantinople in stages during late 1096 and 1097. Their leaders included Godfrey of Bouillon, Raymond of Toulouse, Bohemond of Taranto, Robert of Normandy and others. Emperor Alexios I sought to manage the expedition because he wanted to recover Byzantine territories while preventing the establishment of independent western states inside his empire. The crusader leaders generally agreed to return captured Byzantine territories, although disputes later emerged over the practical meaning of these commitments.
The first major operation was the siege of Nicaea in 1097. Byzantine forces participated in the operation, and the city surrendered to the emperor rather than being captured and looted by the crusaders. This outcome created some resentment among crusaders who had expected direct access to the city's wealth.
After Nicaea, the crusader army moved across Anatolia and encountered a large Seljuk force at Dorylaeum in July 1097. The crusader vanguard came under heavy attack and formed a defensive position while the rest of the army arrived. The battle was eventually won by the crusaders, but the campaign continued to impose severe hardships. The army crossed dry and mountainous territory where water and food were limited. Horses and other animals died in large numbers, reducing the effectiveness of cavalry.
Many participants also became ill or deserted. These logistical problems were among the greatest threats facing the expedition. The crusaders were not operating in a region where they possessed established supply bases, and their ability to continue depended on capturing provisions, obtaining assistance and maintaining cohesion among several independent contingents.
The siege of Antioch began in October 1097 and lasted for approximately eight months. Antioch was a major fortified city and an important strategic centre. The crusaders constructed siege works and attempted to prevent supplies from entering, but the siege itself created severe shortages within the Christian army. Hunger, disease and political disagreements increased. In June 1098, the crusaders gained access to the city after Bohemond obtained assistance from a guard who provided information about a route into the fortifications.
The city was captured, but the victory immediately created a new crisis because a large Muslim relief army approached. The crusaders became trapped inside Antioch and faced starvation. They eventually defeated the relief force on 28 June 1098. The capture of Antioch was a major strategic victory but also caused a serious dispute over control of the city, with Bohemond claiming it rather than returning it to Byzantine authority.
After Antioch, the crusaders spent additional time in the region before continuing towards Jerusalem. The expedition had already suffered enormous losses, and some leaders had established themselves in newly conquered territories. The army that eventually moved south was therefore smaller and more fragmented than the force that had originally arrived. Crusaders captured or negotiated with several coastal and inland settlements as they moved towards the Holy Land.
Jerusalem was controlled by the Fatimid Caliphate of Egypt at the time, rather than by the Seljuk authorities who had previously controlled it. The Fatimids had captured Jerusalem from the Seljuks shortly before the crusaders arrived. This illustrates the complex political situation of the region. The crusaders were not fighting one unified Muslim state but were operating among competing Muslim powers with different interests.
The siege of Jerusalem began in June 1099. The crusaders initially lacked enough timber to construct effective siege equipment, but supplies obtained from the coast enabled them to build siege towers and other devices. Religious ceremonies and fasting accompanied the preparations. On 15 July, crusader forces breached the city's defences and entered Jerusalem. Large numbers of inhabitants were killed in the ensuing violence, including Muslims and Jews, while some people sought refuge in religious or fortified buildings.
Contemporary accounts differ in detail, and precise casualty figures cannot be established reliably. The conquest was presented by crusaders as the fulfilment of the expedition's religious objective. The event was nevertheless a major episode of mass violence and had lasting significance in Christian and Muslim historical memory.
Following the capture of Jerusalem, the crusaders established political institutions in the conquered territories. Godfrey of Bouillon became the leading ruler in Jerusalem and was associated with the title Defender of the Holy Sepulchre rather than initially using the title king. The Kingdom of Jerusalem later became a monarchy, while other crusader states developed at Edessa, Antioch and Tripoli.
These states required continuing military support because they were surrounded by Muslim powers and possessed relatively small populations of western European settlers. Their survival depended on castles, fortified cities, alliances with local communities, maritime supply from Europe and later crusading expeditions. The First Crusade therefore did not end simply with the capture of Jerusalem. It created a new political order that generated further warfare and contributed directly to the later Second, Third and subsequent Crusades.
