The First Crusade (1096–1099) was the first of a series of religious wars initiated, supported, and sometimes directed by the Latin Church in the medieval period. The initial objective was the recovery of the Holy Land from Islamic rule. These campaigns were subsequently given the name crusades. The earliest initiative for the First Crusade began in 1095 when the Byzantine Emperor, Alexios I Komnenos, requested military support from the Council of Piacenza in the Byzantine Empire's conflict with the Seljuk-led Turks. This was followed later in the year by the Council of Clermont, during which Pope Urban II supported the Byzantine request for military assistance and also urged faithful Christians to undertake an armed pilgrimage to Jerusalem.
This call was met with an enthusiastic popular response across all social classes in western Europe. Mobs of predominantly poor Christians numbering in the thousands, led by Peter the Hermit, a French priest, were the first to respond. What has become known as the People's Crusade passed through Germany and indulged in wide-ranging anti-Jewish activities and massacres. On leaving Byzantine-controlled territory in Anatolia, they were annihilated in a Turkish ambush at the Battle of Civetot in October 1096.
In what has become known as the Princes' Crusade, members of the high nobility and their followers embarked in late summer 1096 and arrived at Constantinople between November and April the following year. This was a large feudal host led by notable Western European princes: southern French forces under Raymond of Toulouse and Adhemar of Le Puy; men from Upper and Lower Lorraine led by Godfrey of Bouillon and his brother Baldwin of Boulogne; Italo-Norman forces led by Bohemond of Taranto and his nephew Tancred; as well as various contingents consisting of northern French and Flemish forces under Robert II of Normandy, Stephen of Blois, Hugh of Vermandois, and Count Robert of Flanders. In total and including non-combatants, the army is estimated to have numbered as many as 100,000.
The crusaders marched into Anatolia. While the Seljuk Sultan of Rûm, Kilij Arslan, was away resolving a dispute, a Frankish siege and Byzantine naval assault captured Nicea in June 1097. In marching through Anatolia, the crusaders suffered starvation, thirst, and disease before encountering the Turkish lightly armoured mounted archers at the Battle of Dorylaeum. Baldwin left with a small force to establish the County of Edessa, the first Crusader state, and Antioch was captured in June 1098. Jerusalem was reached in June 1099 and the city was taken by assault on 7 July 1099, during which its defenders were massacred. A counterattack was repulsed at the Battle of Ascalon. After this the majority of the crusaders returned home.
Four Crusader states were established in the Near East: the County of Edessa, the Principality of Antioch, the Kingdom of Jerusalem, and the County of Tripoli. The crusader presence remained in the region in some form until the city of Acre fell in 1291, leading to the rapid loss of all remaining territory in the Levant. There were no further substantive attempts to recover the Holy Land after this.
Christianity had been adopted throughout the Roman Empire in Late Antiquity. Muhammad founded the Islamic religion in the 7th century leading to the conquest by Muslim Arabs of territory that ranged from the Indus in the east, across North Africa to the Iberian Peninsula in the West. Syria, Egypt, and North Africa were taken from the Byzantine Empire. It was political and religious fragmentation that brought this expansion to an end. Shia Islam—the belief system that only descendants of Muhammad's cousin and son-in-law, Ali, and daughter, Fatimah, could lawfully be caliph— emerged leading a split with Sunni Islam on theology, ritual and law. Muslim Iberia became independent in modern Spain and Portugal from the 8th century. The Shi'ite Fatimid dynasty ruled North Africa, swathes of Western Asia including Jerusalem, Damascus and parts of the Mediterranean coastline from 969. The Muslim rulers did not require total submission to Islam from Jews or Christians because they were considered People of the Book or dhimmi. As such they could continue following their faiths on payment of a poll tax. In the Near East a minority Muslim elite ruled over indigenous Christians—Greeks, Armenians, Syrians and Copts.
The causes of the First Crusade are widely debated among historians. While the relative weight or importance of the various factors may be the subject of ongoing disputes, it is clear that the First Crusade came about from a combination of factors earlier in the 11th century in both Europe and the Near East. In Western Europe, Jerusalem was increasingly seen as worthy of penitential pilgrimages. The Seljuk hold on Jerusalem was weak, and the group lost the city to the Fatimids, and returning pilgrims, such as the Great German Pilgrimage of 1064–1065, reported difficulties and the oppression of Christians. The Byzantine need for military support coincided with an increase in the willingness of the western European warrior class to accept papal military command. Western Christians wanted a more effective church and demonstrated an increased piety. From 1000 there was an increasing number of pilgrimages to the Holy Land using safer routes through Hungary. The knighthood and aristocracy developed new devotional and penitential practises that created a fertile ground for crusading recruitment.
The motivation of the Crusaders is unknown. There may have been a spiritual dimension seeking absolution through warfare. At one time historian Georges Duby's theory that crusades offered economic and social opportunity for younger, aristocratic landless sons was popular amongst historians but this was challenged because it does not account for the wider kinship groups in Germany and Southern France. Gesta Francorum talks about the opportunity for plunder and "great booty". Adventure was another explanation including the enjoyment of warfare. As was the fact that many crusaders had no choice as they obliged to follow their feudal lords.
Situation in Europe
Early Christians were used to the use of violence for communal purposes. A Christian theology of war inevitably evolved from when Roman citizenship and Christianity became linked. Citizens were required to fight against the Empire's enemies. Dating from the works of the 4th-century theologian Augustine a doctrine of holy war developed. Augustine wrote that an aggressive war was sinful, but a "just war" could be rationalised if proclaimed by a legitimate authority such as a king or bishop, it was defensive or for the recovery of lands, and a it did not involve excessive violence. The breakdown of the Carolingian Empire in Western Europe created a warriors caste who now had little to do but fight among themselves. Violent acts were commonly used for dispute resolution, and the papacy attempted to mitigate it. Historians, such as Carl Erdmann, believed that the Peace and Truce of God movements restricted conflict between Christians from the 10th century and the influence of these is apparent in Pope Urban II's speeches. But later historians, such as Marcus Bull, assert that the movements' effectiveness were limited and had died out completely by the time of the First Crusade.
By the start of the 11th century, the influence of the papacy had declined to that of little more than a localised bishopric. In the period from around 1050 until 1080 it was the Gregorian Reform movement that developed increasingly assertive policies, eager to increase its power and influence. This prompted conflict with eastern Christians rooted in the doctrine of papal supremacy. The Eastern church viewed the pope as only one of the five patriarchs of the Church, alongside the Patriarchates of Alexandria, Antioch, Constantinople and Jerusalem. In 1054 differences in custom, creed and practice spurred Pope Leo IX to send a legation to the Patriarch of Constantinople, which ended in mutual excommunication and an East–West Schism.
Pope Alexander II developed recruitment systems via oaths for military resourcing that Gregory VII further extended across Europe.  These were deployed by the Church in the Christian conflicts with Muslims during in the 11th century in the Iberian Peninsula and in campaign against the Emirate of Sicily Gregory VII went further in 1074, planning a display of military power to reinforce the principle of papal sovereignty in a holy war supporting Byzantium against the Seljuks, but was unable to build support for this. Theologian Anselm of Lucca took the decisive step towards an authentic crusader ideology, stating that fighting for legitimate purposes could result in the remission of sins.
On the Iberian Peninsula there was no significant Christian polity. The Christian realms of León, Navarre and Catalonia lacked a common identity and shared history based on tribe or ethnicity so they frequently united and divided during the 11th and 12th centuries. Although small, all developed an aristocratic military technique and in 1031 the disintegration of the Caliphate of Córdoba in southern Spain created the opportunity for the territorial gains that later became known as the Reconquista. In 1063 William VIII of Aquitaine led a combined force of French, Aragonese and Catalan knights to take the city of Barbastro that had been in Muslim hands since the year 711. This had the full support of Pope Alexander II, a Truce of God was declared in Catalonia and indulgences were granted to the participants. It was a holy war but differed from the First Crusade as there was no pilgrimage, no vow and no formal authorisation by the church. Shortly before the First Crusade, Pope Urban II had encouraged the Iberian Christians to take Tarragona, using much of the same symbolism and rhetoric that was later used to preach the crusade to the people of Europe.
The Italo-Normans were successful in seizing much of Southern Italy and Sicily from the Byzantines and North African Arabs in the decades before the First Crusade. This brought them into conflict with the Papacy leading to a campaign against them by Pope Leo IX who they defeated at Civitate, although when they invaded Muslim Sicily in 1059 they did so under a papal banner: the lnvexillum sancti Petri or banner of St Peter. Robert Guiscard captured the Byzantine city of Bari in 1071 and campaigned along the Eastern Adriatic coast around Dyrrachium in 1081 and 1085. 
Situation in the East
Compared with Western Europe the Byzantine Empire and the Islamic world were historic centres of wealth, culture and military power. As such, the west was viewed as a backwater that presented negligible threat. Under Basil II the territorial recovery of the Empire reached its furthest extent in 1025. The Empire's frontiers stretched east to Iran, Bulgaria was under control as was much of southern Italy and piracy in the Mediterranean Sea had been suppressed. Relations with the Empire's Islamic neighbours were no more quarrelsome than relations with the Slavs or Western Christians. Normans in Italy; Pechenegs, Serbs and Cumans to the north; and Seljuk Turks in the east were all in competition with the Empire and to meet these challenges the emperors recruited mercenaries, even on occasions from their enemies.
The first waves of Turkic migration into the Middle East enjoined Arab and Turkic history from the 9th century. The status quo in Western Asia was challenged by later waves of Turkish migration, particularly the arrival of the Seljuk Turks in the 10th century. These were a minor ruling clan from Transoxania. They converted to Islam and migrated into Iran to seek their fortune. In the following two decades they conquered Iran, Iraq and the Near East. The Seljuks and their followers were Sunni Muslims which led to conflict in Palestine and Syria with the Shi'ite Fatimids. The Seljuks nomads, Turkish speaking and occasionally shamanistic. Behaviours that were very different from those of their sedentary, Arabic speaking subjects. This was a difference that weakened power structures when combined with the Seljuks habitual governance of territory based on political preferment and competition between independent princes rather than geography. Byzantine Emperor Romanos IV Diogenes attempted to suppress the Seljuks sporadic raiding in 1071 but was defeated at the Manzikert. Historians once considered this a pivotal event, but the battle is now considered as only one further step in the expansion of the Great Seljuk Empire.
From 1092 the status quo in the Middle East disintegrated following the death of the vizier and effective ruler of the Seljuk Empire, Nizam al-Mulk. This was closely followed by the deaths of the Seljuk Sultan Malik-Shah and the Fatimid khalif, Al-Mustansir Billah. The Islamic historian Carole Hillenbrand has described this as analogous to the fall of the Iron Curtain in 1989 with the phrase "familiar political entities gave way to disorientation and disunity". The confusion and division meant the Islamic world disregarded the world beyond; this made it vulnerable to, and surprised by, the First Crusade. Malik-Shah was succeeded in the Anatolian Sultanate of Rum by Kilij Arslan I, and in Syria by his brother Tutush I. When Tutush died in 1095 his sons Fakhr al-Mulk Radwan and Duqaq inherited Aleppo and Damascus respectively, further dividing Syria amongst emirs antagonistic towards each other, as well as Kerbogha, the atabeg of Mosul. Egypt and much of Palestine were controlled by the Arab Shi'ite Fatimid Caliphate The Fatimids, under the nominal rule of caliph al-Musta'li but actually controlled by vizier al-Afdal Shahanshah, lost Jerusalem to the Seljuqs in 1073 but succeeded in recapturing the city in 1098 from the Artuqids, a smaller Turkish tribe associated with the Seljuqs, just before the arrival of the crusaders.
Council of Clermont
Byzantine emperor Alexios I Komnenos, worried about the advances of the Seljuqs in the aftermath of the Battle of Manzikert, who had reached as far west as Nicaea, sent envoys to the Council of Piacenza in March 1095 to ask Pope Urban II for aid against the invading Turks.
Urban responded favourably, perhaps hoping to heal the Great Schism of forty years earlier, and to reunite the Church under papal primacy by helping the Eastern churches in their time of need. Alexios and Urban had previously been in close contact in 1089 and after, and had discussed openly the prospect of the (re)union of the Christian church. There were signs of considerable co-operation between Rome and Constantinople in the years immediately before the crusade.
In July 1095, Urban turned to his homeland of France to recruit men for the expedition. His travels there culminated in the ten-day Council of Clermont, where on Tuesday 27 November he gave an impassioned sermon to a large audience of French nobles and clergy. There are five versions of the speech recorded by people who may have been at the council (Baldric of Dol, Guibert of Nogent, Robert the Monk, and Fulcher of Chartres) or who went on crusade (Fulcher and the anonymous author of the Gesta Francorum), as well as other versions found in later historians (such as William of Malmesbury and William of Tyre). All of these versions were written after Jerusalem had been captured. Thus it is difficult to know what was actually said and what was recreated in the aftermath of the successful crusade. The only contemporary records are a few letters written by Urban in 1095.
The five versions of the speech differ widely from one another in regard to particulars, but all versions except that in the Gesta Francorum agree that Urban talked about the violence of European society and the necessity of maintaining the Peace of God; about helping the Greeks, who had asked for assistance; about the crimes being committed against Christians in the east; and about a new kind of war, an armed pilgrimage, and of rewards in heaven, where remission of sins was offered to any who might die in the undertaking. They do not all specifically mention Jerusalem as the ultimate goal. However, it has been argued that Urban's subsequent preaching reveals that he expected the expedition to reach Jerusalem all along. According to one version of the speech, the enthusiastic crowd responded with cries of Deus vult! ("God wills it!").
The great French nobles and their trained armies of knights, however, were not the first to undertake the journey towards Jerusalem. Urban had planned the departure of the first crusade for 15 August 1096, the Feast of the Assumption, but months before this, a number of unexpected armies of peasants and petty nobles set off for Jerusalem on their own, led by a charismatic priest called Peter the Hermit. Peter was the most successful of the preachers of Urban's message, and developed an almost hysterical enthusiasm among his followers, although he was probably not an "official" preacher sanctioned by Urban at Clermont. It is commonly believed that Peter's followers purely consisted of a massive group of untrained and illiterate peasants who did not even have any idea where Jerusalem was, but there were also many knights among the peasants, including Walter Sans Avoir, who was lieutenant to Peter and led a separate army.
Lacking military discipline, in what likely seemed to the participants a strange land (Eastern Europe), Peter's fledgling army quickly found itself in trouble despite the fact they were still in Christian territory. The army led by Walter fought with the Hungarians over food at Belgrade, but otherwise arrived in Constantinople unharmed. Meanwhile, the army led by Peter, which marched separately from Walter's army, also fought with the Hungarians, and may have captured Belgrade. At Nish the Byzantine governor tried to supply them, but Peter had little control over his followers and Byzantine troops were needed to quell their attacks. Peter arrived at Constantinople in August, where his army joined with the one led by Walter, which had already arrived, as well as separate bands of crusaders from France, Germany, and Italy. Another army of Bohemians and Saxons did not make it past Hungary before splitting up.
This unruly mob began to attack and pillage outside the city in search of supplies and food, prompting Alexios to hurriedly ferry the gathering across the Bosporus one week later. After crossing into Asia Minor, the crusaders split up and began to pillage the countryside, wandering into Seljuq territory around Nicaea. The greater experience of the Turks was overwhelming; and most of this group of the crusaders were massacred because of it. Some Italian and German crusaders were defeated and killed at Xerigordon at the end of August. Meanwhile, Walter and Peter's followers, who, although for the most part untrained in battle but led by about 50 knights, fought a battle against the Turks at Civetot in October. The Turkish archers destroyed the crusader army, and Walter was among the dead. Peter, who was absent in Constantinople at the time, later joined the main crusader army, along with the few survivors of Civetot.
At a local level, the preaching of the First Crusade ignited the Rhineland massacres perpetrated against Jews, which some historians have deemed "the first Holocaust". At the end of 1095 and beginning of 1096, months before the departure of the official crusade in August, there were attacks on Jewish communities in France and Germany. In May 1096, Emicho of Flonheim (sometimes incorrectly known as Emicho of Leiningen) attacked the Jews at Speyer and Worms. Other unofficial crusaders from Swabia, led by Hartmann of Dillingen, along with French, English, Lotharingian and Flemish volunteers, led by Drogo of Nesle and William the Carpenter, as well as many locals, joined Emicho in the destruction of the Jewish community of Mainz at the end of May. In Mainz, one Jewish woman killed her children rather than see them killed; the chief rabbi, Kalonymus Ben Meshullam, committed suicide in anticipation of being killed. Emicho's company then went on to Cologne, and others continued on to Trier, Metz, and other cities. Peter the Hermit may have been involved in violence against the Jews, and an army led by a priest named Folkmar also attacked Jews further east in Bohemia.
King Coloman the Learned, had to deal with the problems that the armies of the First Crusade caused during their march across Hungary towards the Holy Land in 1096. He defeated and massacred two crusader hordes to prevent their pillaging raids in Kingdom of Hungary. Emicho's army eventually continued into Hungary but was defeated by the army of Coloman. Emicho's followers dispersed; some eventually joined the main armies, although Emicho himself went home. Many of the attackers seem to have wanted to force the Jews to convert, although they were also interested in acquiring money from them. Physical violence against Jews was never part of the church hierarchy's official policy for crusading, and the Christian bishops, especially the Archbishop of Cologne, did their best to protect the Jews. A decade before, the Bishop of Speyer had taken the step of providing the Jews of that city with a walled ghetto to protect them from Christian violence and given their chief Rabbis the control of judicial matters in the quarter. Nevertheless, some also took money in return for their protection. The attacks may have originated in the belief that Jews and Muslims were equally enemies of Christ, and enemies were to be fought or converted to Christianity. Godfrey of Bouillon was rumoured to have extorted money from the Jews of Cologne and Mainz, and many of the Crusaders wondered why they should travel thousands of miles to fight non-believers when there were already non-believers closer to home.
The four main crusader armies left Europe around the appointed time in August 1096. They took different paths to Constantinople and gathered outside its city walls between November 1096 and April 1097; Hugh of Vermandois arrived first, followed by Godfrey, Raymond, and Bohemond. This time, Emperor Alexios was more prepared for the crusaders; there were fewer incidents of violence along the way. It is impossible to estimate the numbers involved. Some historians put a figure of 70,000 to 80,000 on the number who left Western Europe in the year after Clermont, and more joined in the three-year duration. Estimates for the number of Knights range from 7,000 to 10,000; 35,000 to 50,000 foot soldiers; and including non-combatants a total of 60,000 to 100,000. King Coloman of Hungary allowed Godfrey of Bouillon and his troops to cross Hungary only after Godfrey offered his brother, Baldwin, as a hostage to guarantee his troops' good conduct. In this way king Coloman wanted to prevent the pillage of the Crusader army.
Urban's speech had been well-planned: he had discussed the crusade with Adhemar of Le Puy and Raymond IV, Count of Toulouse, and instantly the expedition had the support of two of southern France's most important leaders. Adhemar himself was present at the council and was the first to "take the cross". During the rest of 1095 and into 1096, Urban spread the message throughout France, and urged his bishops and legates to preach in their own dioceses elsewhere in France, Germany, and Italy as well. However, it is clear that the response to the speech was much greater than even the Pope, let alone Alexios, expected. On his tour of France, Urban tried to forbid certain people (including women, monks, and the sick) from joining the crusade, but found this nearly impossible. In the end, most who took up the call were not knights, but peasants who were not wealthy and had little in the way of fighting skills, in an outpouring of a new emotional and personal piety that was not easily harnessed by the ecclesiastical and lay aristocracy. Typically, preaching would conclude with every volunteer taking a vow to complete a pilgrimage to the Church of the Holy Sepulchre; they were also given a cross, usually sewn onto their clothes.
As Thomas Asbridge wrote, "Just as we can do nothing more than estimate the number of thousands who responded to the crusading ideal, so too, with the surviving evidence, we can gain only a limited insight into their motivation and intent." Previous generations of scholars argued that the crusaders were motivated by greed, hoping to find a better life away from the famines and warfare occurring in France, but as Asbridge notes, "This image is ... profoundly misleading." He argues that greed was unlikely to have been a major factor because of the extremely high cost of travelling so far from home, and because almost all of the crusaders eventually returned home after completing their pilgrimage rather than trying to carve out possessions for themselves in the Holy Land. It is difficult or impossible to assess the motives of the thousands of poor for whom there is no historical record, or even those of important knights, whose stories were usually retold by monks or clerics. As the secular medieval world was so deeply ingrained with the spiritual world of the church, it is quite likely that personal piety was a major factor for many crusaders.
Despite this popular enthusiasm, however, Urban ensured that there would be an army of knights, drawn from the French aristocracy. Aside from Adhemar and Raymond, other leaders he recruited throughout 1096 included Bohemond of Taranto, a southern Italian ally of the reform popes; Bohemond's nephew Tancred; Godfrey of Bouillon, who had previously been an anti-reform ally of the Holy Roman Emperor; his brother Baldwin of Boulogne; Hugh I, Count of Vermandois, brother of the excommunicated Philip I of France; Robert Curthose, brother of William II of England; and his relatives Stephen II, Count of Blois and Robert II, Count of Flanders. The crusaders represented northern and southern France, Flanders, Germany, and southern Italy, and so were divided into four separate armies that were not always cooperative, though they were held together by their common ultimate goal.
The crusade was led by some of the most powerful nobles of France, who left everything behind, and it was often the case that entire families went on crusade at their own great expense. For example, Robert of Normandy loaned the Duchy of Normandy to his brother William II of England, and Godfrey sold or mortgaged his property to the church. According to Tancred's biographer, he was worried about the sinful nature of knightly warfare, and was excited to find a holy outlet for violence. Tancred and Bohemond, as well as Godfrey, Baldwin, and their older brother Eustace III, Count of Boulogne, are examples of families who crusaded together. Riley-Smith argues that the enthusiasm for the crusade was perhaps based on family relations, as most of the French crusaders were distant relatives. Nevertheless, in at least some cases, personal advancement played a role in Crusaders' motives. For instance, Bohemond was motivated by the desire to carve himself out a territory in the east, and had previously campaigned against the Byzantines to try to achieve this. The Crusade gave him a further opportunity, which he took after the Siege of Antioch, taking possession of the city and establishing the Principality of Antioch.
The size of the entire crusader army is difficult to estimate; various numbers were given by the eyewitnesses, and equally various estimates have been offered by modern historians. Crusader military historian David Nicolle considers the armies to have consisted of about 30,000–35,000 crusaders, including 5,000 cavalry. Raymond had the largest contingent of about 8,500 infantry and 1,200 cavalry.
The princes arrived in Constantinople with little food and expected provisions and help from Alexios. Alexios was understandably suspicious after his experiences with the People's Crusade, and also because the knights included his old Norman enemy, Bohemond, who had invaded Byzantine territory on numerous occasions with his father, Robert Guiscard, and may have even attempted to organize an attack on Constantinople while encamped outside the city.
The crusaders may have expected Alexios to become their leader, but he had no interest in joining them, and was mainly concerned with transporting them into Asia Minor as quickly as possible. In return for food and supplies, Alexios requested the leaders to swear fealty to him and promise to return to the Byzantine Empire any land recovered from the Turks. Godfrey was the first to take the oath, and almost all the other leaders followed him, although they did so only after warfare had almost broken out in the city between the citizens and the crusaders, who were eager to pillage for supplies. Raymond alone avoided swearing the oath, instead pledging that he would simply cause no harm to the Empire. Before ensuring that the various armies were shuttled across the Bosporus, Alexios advised the leaders on how best to deal with the Seljuq armies that they would soon encounter.
Siege of Nicaea
The Crusader armies crossed over into Asia Minor during the first half of 1097, where they were joined by Peter the Hermit and the remainder of his relatively small army. In addition, Alexios also sent two of his own generals, Manuel Boutoumites and Tatikios, to assist the crusaders. The first objective of their campaign was Nicaea, previously a city under Byzantine rule, but which had become the capital of the Seljuq Sultanate of Rum under Kilij Arslan I. Arslan was away campaigning against the Danishmends in central Anatolia at the time, and had left behind his treasury and his family, underestimating the strength of these new crusaders.
Subsequently, upon the Crusaders' arrival, the city was subjected to a lengthy siege, and when Arslan had word of it he rushed back to Nicaea and attacked the crusader army on 16 May. He was driven back by the unexpectedly large crusader force, with heavy losses being suffered on both sides in the ensuing battle. The siege continued, but the crusaders had little success as they found they could not blockade the lake, which the city was situated on, and from which it could be provisioned. To break the city, Alexios sent the Crusaders' ships rolled over land on logs, and at the sight of them the Turkish garrison finally surrendered on 18 June.
There was some discontent amongst the Franks who were forbidden from looting the city. This was ameliorated by Alexius financially rewarding the crusaders. Later chronicles exaggerate tension between the Greeks and Franks but Stephen of Blois, in a letter to his wife Adela of Blois confirms goodwill and cooperation continued at this point. As Thomas Asbridge writes, "the fall of Nicaea was a product of the successful policy of close co-operation between the crusaders and Byzantium."
Battle of Dorylaeum
At the end of June, the crusaders marched on through Anatolia. They were accompanied by some Byzantine troops under Tatikios, and still harboured the hope that Alexios would send a full Byzantine army after them. They also divided the army into two more-easily managed groups—one contingent led by the Normans, the other by the French. The two groups intended to meet again at Dorylaeum, but on 1 July the Normans, who had marched ahead of the French, were attacked by Kilij Arslan. Arslan had gathered a much larger army than he previously had after his defeat at Nicaea, and now surrounded the Normans with his fast-moving mounted archers. The Normans "deployed in a tight-knit defensive formation", surrounding all their equipment and the non-combatants who had followed them along the journey, and sent for help from the other group. When the French arrived, Godfrey broke through the Turkish lines and the legate Adhemar outflanked the Turks from the rear; thus the Turks, who had expected to destroy the Normans and did not anticipate the quick arrival of the French, fled rather than face the combined crusader army.
The crusaders' march through Anatolia was thereafter unopposed, but the journey was unpleasant, as Arslan had burned and destroyed everything he left behind in his army's flight. It was the middle of summer, and the crusaders had very little food and water; many men and horses died. Fellow Christians sometimes gave them gifts of food and money, but more often than not, the crusaders simply looted and pillaged whenever the opportunity presented itself. Individual leaders continued to dispute the overall leadership, although none of them were powerful enough to take command on their own, as Adhemar was always recognized as the spiritual leader. After passing through the Cilician Gates, Baldwin of Boulogne set off on his own towards the Armenian lands around the Euphrates; his wife, his only claim to European lands and wealth, had died after the battle, giving Baldwin no incentive to return to Europe. Thus, he resolved to seize a fiefdom for himself in the Holy Land. Early in 1098, he was adopted as heir by Thoros of Edessa, a ruler who was disliked by his Armenian subjects for his Greek Orthodox religion. Thoros was later killed, during an uprising that Baldwin may have instigated. Then, in March 1098, Baldwin became the new ruler, thus creating the County of Edessa, the first of the crusader states.
Siege of Antioch
The crusader army, meanwhile, marched on to Antioch, which lay about halfway between Constantinople and Jerusalem. Described by Stephen of Blois as "a city great beyond belief, very strong and unassailable", the idea of taking the city by assault was a discouraging one to the crusaders. Hoping rather to force a capitulation, or find a traitor inside the city—a tactic that had previously seen Antioch change to the control of the Byzantines and then the Seljuq Turks—the crusader army set Antioch to siege on 20 October 1097. Antioch was so large that the crusaders did not have enough troops to fully surround it, and as a result it was able to stay partially supplied.
By January the attritional eight-month siege led to hundreds, or possibly thousands, of crusaders dying of starvation. Adhemar considered this was caused by their sinful nature; woman were expelled from the camp, fasting, prayer, alms giving and procession undertaken. Many, such as Stephen of Blois, deserted. Foraging systems eased the situation, as did supplies from Cicilia, Edessa, through the recently captured ports of Latakia and Port Saint Symeon and in March a small English fleet. The Franks benefited from disunity in the Muslim world and the possible misunderstanding that they were thought to be Byzantine mercenaries. The Seljuk brothers, Duqaq of Syria and Fakhr al-Mulk Radwan of Aleppo dispatched separate relief armies in December and February that if they had been combined would probably have been victorious.
After these failures the Atabeg of Mosul raised a coalition from southern Syria, northern Iraq and Anatolia with the ambition of extending his power from Syria to the Mediterranean sea. Bohemond persuaded the other leaders that if Antioch fell he would keep it for himself and that an Armenian commander of a section of the cities walls had agreed to enable the crusaders to enter. Stephen of Blois had been his only competitor and while deserting his message to Alexius that the cause was lost persuaded the Emperor to halt his advance through Anatolia at Philomelium before returning to Constantinople. Alexius failure to reach the siege was used by Bohemond to rationalise his refusal to return the city to the Empire as promised. The Armenian, Firouz, helped Bohemond and a small party enter the city on the 2nd June and open a gate at which point horns were sounded, the city's Christian majority opened the other gates and the crusaders entered. In the sack they killed most of the Muslim inhabitants and many Christian Greeks, Syrians and Armenians in the confusion.
On 4 June the vanguard of Kerbogha's 40,000 strong army arrived surrounding the Franks. From 10 June for 4 days waves of Kerbogha's men assailed the city walls from dawn until dusk. Bohemond and Adhemar barred the city gates to prevent mass desertions and managed to hold out. Kerbogha then changed tactics to trying to starve the crusaders out. Morale inside the city was low and defeat looked imminent but a peasant visionary called Peter Bartholomew claimed the apostle St Andrew came to him to show the location of the Holy Lance that had pierced Christ on the cross. This supposedly encouraged the crusaders but the accounts are misleading as it was two weeks before the final battle for the city. On 24 June the Franks sought terms for surrender that were refused. On 28 June 1098 at dawn the Franks marched out of the city in four battle groups to engage the enemy. Kerbogha allowed them to deploy with the aim of destroying them in the open. However the discipline of the Muslim army did not hold and a disorderly attack was launched. Unable to overrun a bedraggled force they outnumbered two to one Muslims attacking the Bridge Gate fled through the advancing main body of the Muslim army. With very few casualties the Muslim army broke and fled the battle.
Stephen of Blois, a Crusade leader, was in Alexandretta when he learned of the situation in Antioch. It seemed like their situation was hopeless so he left the Middle East, warning Alexios and his army on his way back to France. Because of what looked like a massive betrayal, the leaders at Antioch, most notably Bohemond, argued that Alexios had deserted the Crusade and thus invalidated all of their oaths to him. While Bohemond asserted his claim to Antioch, not everyone agreed (most notably Raymond of Toulouse), so the crusade was delayed for the rest of the year while the nobles argued amongst themselves. When discussing this period, a common historiographical viewpoint advanced by some scholars is that the Franks of northern France, the Provençals of southern France, and the Normans of southern Italy considered themselves separate "nations", creating turmoil as each tried to increase its individual status. Others argue that while this may have had something to do with the disputes, personal ambition among the Crusader leaders might just be as easily blamed.
Meanwhile, a plague broke out, killing many among the army, including the legate Adhemar, who died on 1 August. There were now even fewer horses than before, and worse, the Muslim peasants in the area refused to supply the crusaders with food. Thus, in December, after the Arab town of Ma'arrat al-Numan was captured following a siege, history describes the first occurrence of cannibalism among the crusaders. Radulph of Caen wrote, "In Ma'arrat our troops boiled pagan adults in cooking pots; they impaled children on spits and devoured them grilled." At the same time, the minor knights and soldiers had become increasingly restless and threatened to continue to Jerusalem without their squabbling leaders. Finally, at the beginning of 1099, the march restarted, leaving Bohemond behind as the first Prince of Antioch.
Continued march to Jerusalem
Proceeding down the Mediterranean coast, the crusaders encountered little resistance, as local rulers preferred to make peace with them and furnish them with supplies rather than fight, with a notable exception of the abandoned siege of Arqa.Iftikhar ad-Daula, the Fatimid governor of Jerusalem, was aware of the arrival of the Crusaders. He expelled all of Jerusalem's Christian inhabitants before the Crusaders' arrival, to avoid the possibility of the city falling due to treason from the inside, and he poisoned most of the wells in the area. The crusaders reached Jerusalem, which had been recaptured from the Seljuqs by the Fatimids only the year before, on 7 June. Many Crusaders wept upon seeing the city they had journeyed so long to reach.
Siege of Jerusalem
Crusaders' arrival at Jerusalem revealed an arid countryside, lacking in water or food supplies. Here there was no prospect of relief, even as they feared an imminent attack by the local Fatimid rulers. There was no hope of trying to blockade the city as they had at Antioch; the crusaders had insufficient troops, supplies, and time. Rather, they resolved to take the city by assault. They might have been left with little choice, as by the time the Crusader army reached Jerusalem, it has been estimated that only about 12,000 men including 1,500 cavalry remained. These contingents, composed of men with differing origins and varying allegiances, were also approaching another low ebb in their camaraderie; e.g., while Godfrey and Tancred made camp to the north of the city, Raymond made his to the south. In addition, the Provençal contingent did not take part in the initial assault on 13 June. This first assault was perhaps more speculative than determined, and after scaling the outer wall the Crusaders were repulsed from the inner one.
After the failure of the initial assault, a meeting between the various leaders was organized in which it was agreed upon that a more concerted attack would be required in the future. On 17 June, a party of Genoese mariners under Guglielmo Embriaco arrived at Jaffa, and provided the Crusaders with skilled engineers, and perhaps more critically, supplies of timber (stripped from the ships) to build siege engines. The Crusaders' morale was raised when a priest, Peter Desiderius, claimed to have had a divine vision, of Bishop Adhemar, instructing them to fast and then march in a barefoot procession around the city walls, after which the city would fall, following the Biblical story of Joshua at the siege of Jericho. After a three-day fast, on 8 July the crusaders performed the procession as they had been instructed by Desiderius, ending on the Mount of Olives where Peter the Hermit preached to them, and shortly afterward the various bickering factions arrived at a public rapprochement. News arrived shortly after that a Fatimid relief army had set off from Egypt, giving the Crusaders a very strong incentive to make another assault on the city.
The final assault on Jerusalem began on 13 July; Raymond's troops attacked the south gate while the other contingents attacked the northern wall. Initially the Provençals at the southern gate made little headway, but the contingents at the northern wall fared better, with a slow but steady attrition of the defence. On 15 July, a final push was launched at both ends of the city, and eventually the inner rampart of the northern wall was captured. In the ensuing panic, the defenders abandoned the walls of the city at both ends, allowing the Crusaders to finally enter.
The massacre that followed the capture of Jerusalem has attained particular notoriety, as a "juxtaposition of extreme violence and anguished faith". The eyewitness accounts from the crusaders themselves leave little doubt that there was great slaughter in the aftermath of the siege. Nevertheless, some historians propose that the scale of the massacre has been exaggerated in later medieval sources.
After the successful assault on the northern wall, the defenders fled to the Temple Mount, pursued by Tancred and his men. Arriving before the defenders could secure the area, Tancred's men assaulted the precinct, butchering many of the defenders, with the remainder taking refuge in the Al-Aqsa Mosque. Tancred then called a halt to the slaughter, offering those in the mosque his protection. When the defenders on the southern wall heard of the fall of the northern wall, they fled to the citadel, allowing Raymond and the Provençals to enter the city. Iftikhar al-Dawla, the commander of the garrison, struck a deal with Raymond, surrendering the citadel in return for being granted safe passage to Ascalon.
The slaughter continued for the rest of the day; Muslims were indiscriminately killed, and Jews who had taken refuge in their synagogue died when it was burnt down by the Crusaders. The following day, Tancred's prisoners in the mosque were slaughtered. Nevertheless, it is clear that some Muslims and Jews of the city survived the massacre, either escaping or being taken prisoner to be ransomed. The Eastern Christian population of the city had been expelled before the siege by the governor, and thus escaped the massacre.
Establishment of the Kingdom of Jerusalem
On 22 July, a council was held in the Church of the Holy Sepulchre to establish governance for Jerusalem. The death of the Greek Patriarch meant there was no obvious ecclesiastical candidate to establish a religious lordship, as a body of opinion maintained. Although Raymond of Toulouse could claim to be the pre-eminent crusade leader from 1098 his support had waned since his failed attempts to besiege Arqa and create his own realm. This may have been why he piously refused the crown on the grounds that it could only be worn by Christ. It may also have been an attempt to persuade others to reject the title, however Godfrey was already familiar with such a position and more persuasive was probably the large army of troops from Lorraine in Jerusalem, led by him and his brothers, Eustace and Baldwin, who were vassals of the Ardennes-Bouillion dynasty. Therefore, Godfrey was elected, accepting the title Defender of the Holy Sepulchre and took secular power. Raymond was incensed at this development, attempted to seize the Tower of David before leaving the city.
Battle of Ascalon
In August vizier al-Afdal Shahanshah landed a force of 20,000 North Africans at Ascalon. Geoffrey and Raymond marched out to meet this force on 9 August to prevent being besieged with a force of only 1,200 knights and 9,000 foot soldiers. Outnumbered two to one the Franks launched a surprise dawn attack and routed the over confident and unprepared Muslim force. The opportunity was wasted though, as squabbling between Raymond and Godfrey prevented an attempt by the city's garrison to surrender to the more trusted Raymond. The city remained in Muslim hands and a military threat to the nascent kingdom.
Aftermath and legacy
The majority of crusaders now considered their pilgrimage complete and returned home. Only 300 knights and 2,000 infantry remained to defend Palestine. It was the support of the knights from Lorraine that enabled Godfrey to take secular leadership of Jerusalem, over the claims of Raymond. When he dies a year later these same Lorrainers thwarted the papal legate, Dagobert of Pisa's plans for Jerusalem becoming a theocracy and instead made Baldwin the first Latin king of Jerusalem. Bohemond returned to Europe to fight the Byzantines from Italy but he was defeated in 1108 at Dyrrhachium. After Raymond's death, his heirs captured Tripoli with the Genoese support.  Relations between the newly created Crusader states of the county of Edessa and the principality of Antioch were variable: they fought together in the crusader defeat at the Battle of Harran; but the Antiocheans claimed suzerainty and blocked the return of Baldwin after his capture at the battle. The Franks became fully engaged in Near East politics with the result that Muslims and Christians often fought on opposing sides. The expansion of Antioch's territorial expansion ended in 1119 with the major defeat to the Turks at the Field of Blood.
However, there were many who had gone home before reaching Jerusalem, and many who had never left Europe at all. When the success of the crusade became known, these people were mocked and scorned by their families and threatened with excommunication by the Pope. Back at home in Western Europe, those who had survived to reach Jerusalem were treated as heroes. Robert of Flanders was nicknamed "Hierosolymitanus" (Robert of Jerusalem) thanks to his exploits. Among the crusaders in the Crusade of 1101 were Stephen II, Count of Blois and Hugh of Vermandois, both of whom had returned home before reaching Jerusalem. This crusade was almost annihilated in Asia Minor by the Seljuqs, but the survivors helped to reinforce the kingdom upon their arrival in Jerusalem.
There is limited written evidence of the Islamic reaction dating from before 1160, but what there is indicates the crusade was barely noticed. This may be the result of a cultural misunderstanding in that the Turks and Arabs did not recognise the crusaders as religiously motivated warriors with motivations of conquest and settlement. The assumption was the crusaders were just the latest in a long line of Byzantine mercenaries. Also the Islamic world remained divided between rival rulers in Cairo, Damascus, Aleppo and Baghdad. There was no pan-Islamic counter-attack giving the crusaders the opportunity to consolidate.
Latin Christendom was amazed by the success of the First Crusade for which the only credible explanation was it was the work of God. If the crusade had failed it is likely that the paradigm of crusading would have become obsolete. Instead, this form of religious warfare was popular for centuries and the crusade itself became one of the most written about historic events of the medieval period. One of the most influential and earliest works was the anonymous Gesta Francorum or Deeds of the Franks. It was probably written by an Italo-Norman noble in Jerusalem from 1100. It was a new type of epic and heroic narrative, rather than chronicle, history callen a historia. Raymond of Aquilers, Fulcher of Chartres and Peter Tudebode used this as a template for their own versions.
These sources were in turn rewritten by three Benedictine northern French monks; Robert of Rheims, Guibert of Nogent and Baldric of Bourgueil. Not only did they polish the language used, they also added their own events. Robert's additions included Biblical references, miraculous events and expanded the part played by Pope Urban to the point where he instigated, directed, and legitimised towards the objective that was always Jerusalem. The popularity of these works shaped how crusading was viewed in the medieval mind and Robert's work was the source of the 10,000 line chanson de geste, epic poem, about the crusade called Chanson d'Antioche. The crusades in memory were shaped by these works; with Godfrey as the primary leader, the miracles of the Holy Lance and revelling in the violent sack of Jerusalem.
Steven Runciman's literary three-volume work A History of the Crusades, published between 1951 and 1954, significantly shaped the popular perception of the crusades in the later 20th century. However, academic crusade historians now consider it dated, polemical, derivative, tendentious and misleading. Stylistically it owes much in style to Gibbons, Greek specialist George Finlay and his Cambridge tutor J. B. Bury. Runciman used literary devices and even invented events. His coverage of the First Crusade is largely based on Histoire de la Première Croisade jusqu'à l'élection de Godefroi de Bouillon by Ferdinand Chalandon. Runciman viewed the crusade as a "clash of civilisations" using broad stereotypes: western Europeans were ignorant, rough and rude; Byzantine Greeks were cultivated, sophisticated and decadent; Muslims had tolerance, faith and martial vigour. Jonathan Riley-Smith quotes Runciman as saying "[he] was not an historian, but a writer of literature".
Historians of the second half of the 20th century, such as Speros Vryonis (1971), have emphasized the importance of the military threat of Islamic expansion and the atrocities and attacks against Christians in Anatolia and the Levant. Moshe Gil (1997) argues against Runciman on the basis of contemporary Jewish Cairo Geniza documents, as well as later Muslim accounts, concluding that the Seljuq invasion of Anatolia and the occupation of Palestine (c. 1073–1098) was a period of "slaughter and vandalism, of economic hardship, and the uprooting of populations". Thomas F. Madden argues that it was most importantly a pious struggle to liberate fellow Christians, who, Madden claims, "had suffered mightily at the hands of the Turks". This argument distinguishes the relatively recent violence and warfare that followed the conquests of the Turks from the general advance of Islam in the early medieval period, the significance of which had been dismissed by Runciman and Asbridge. Christopher Tyerman (2006) attempted a resolution by arguing for compound causes, presenting the First Crusade as developing out of the Western church reform and theories of holy war as much as being a response to conflicts with the Islamic world throughout Europe and the Middle East. In the view of Jonathan Riley-Smith (2005), additional contingencies such as poor harvests, overpopulation, and a pre-existing movement towards colonizing the frontier areas of Europe have also contributed to the crusade; however, he also takes care to say that "most commentators then and a minority of historians now have maintained that the chief motivation was a genuine idealism". Peter Frankopan (2012) has argued that the First Crusade has been fundamentally distorted by the attention paid by historians to western (Latin) sources, rather than Greek, Syriac, Armenian, Arabic and Hebrew material from the late 11th and 12th centuries. The expedition to Jerusalem, he argues, was conceived of not by the Pope but by the Emperor Alexios I Komnenos, in response to a dramatic deterioration of Byzantium's position in Asia Minor and also as a result of a state of near-anarchy at the imperial court where plans to depose Alexios or even murder him were an open secret by 1094. The appeal to Pope Urban II was a desperate move to shore up Emperor and Empire. Frankopan further argues that the primary military targets of the First Crusade in Asia Minor — Nicaea and Antioch — required large numbers of soldiers with experience in siege warfare, precisely the type of force recruited by Urban in France in his call to arms of 1095/6.
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