The crusades were a series of religious wars sanctioned by the Latin Church in the medieval period. The best-known crusades are the campaigns in the eastern Mediterranean aimed at recovering the Holy Land from Muslim rule. The term crusade is now also applied to other church-sanctioned and even non-religious campaigns. These were fought for a variety of reasons including the suppression of paganism and heresy, the resolution of conflict among rival Roman Catholic groups, or for political and territorial advantage. At the time of the early crusades the word did not exist, and it only became the leading descriptive term in English around the year 1760.

Pope Urban II preached for the First Crusade in 1095, at the Council of Clermont. He encouraged military support for Emperor Alexios I who needed reinforcements for the Byzantine Empire’s conflict with westward migrating Turks colonising Anatolia. Urban aimed to guarantee pilgrim access to the eastern Mediterranean holy sites under Muslim control. Urban's strategy may have been to establish himself as head of the unified Church, uniting the eastern and western branches that had been divided by the East–West Schism. The crusade established four crusader states in the eastern Mediterranean: the County of Edessa, the Principality of Antioch, the Kingdom of Jerusalem and the County of Tripoli. The enthusiastic response to Urban's preaching across all social strata in western Europe established a precedent for further crusades. Volunteers became crusaders by taking a public vow and receiving plenary indulgences from the Church. Some were hoping for a mass ascension into heaven at Jerusalem or God's forgiveness for their sins. Others participated to satisfy feudal obligations, obtain glory and honour, or to seek economic and political gain.

Conventionally an arbitrary system devised by the historian Charles Mills in 1820 is used to number nine distinct campaigns as Crusades. The Second Crusade achieved little beyond the capture of Lisbon from the Moors by the English. The Third Crusade failed to recapture Jerusalem. The Fourth diverted to sack Constantinople. The Fifth was defeated in Egypt. The Sixth regained Jerusalem by negotiation for a period of fifteen years. The Seventh also ended in defeat in Egypt and the Eighth failed in Tunis. The Ninth is sometimes considered part of the Eighth and is of minor importance, only notable for the presence of Prince Edward, the future king of England. The last of the Eastern Crusader cities fell in 1291 and there were no more crusades to recover the Holy Land. Territorial gains lasted longer in northern and western Europe. Crusades brought all the north-east Baltic and the neighbouring Slavic tribes, known as Wends, under Catholic control in the late 12th century. The Teutonic Order created a crusader state in Prussia in the early 13th century, and the French monarchy used the Albigensian Crusade to extend the kingdom to the Mediterranean Sea. The rise of the Ottoman Empire in the late 14th century prompted a Catholic response which led to further defeats at Nicopolis and Varna. In the 15th century the pivotal events in Christian–Islamic relations were marked by two events: the Fall of Constantinople to the Ottomans, and a conclusive victory for the Spanish over the Moors in the conquest of Granada. The idea of crusading did continue, not least in the form of the Knights Hospitaller, until the end of the 18th century, but the focus of western European interest moved to the New World.

Modern historians hold widely varying opinions of the crusaders.

To some, their conduct was incongruous with the stated aims and the implied moral authority of the papacy. Muslims were killed in large numbers on many occasions, as were Christians of other denominations. The crusades had a profound impact on western civilisation. The republics of Genoa and Venice flourished, establishing communes in the Crusader States and expanding trade with eastern markets. Venice gained a maritime Empire. The collective identity of the Latin Church was consolidated under papal leadership by the ideological developments of Crusading and these reinforced the connection between western Christendom, feudalism and militarism. Accounts of crusading heroism, chivalry and piety influenced Medieval romance, philosophy and literature.

The term crusade used in modern historiography at first referred to the wars in the Holy Land beginning in 1095. The range of events to which the term has been applied has been greatly extended, so its use can create a misleading impression of coherence, particularly regarding the early crusades. The Latin terms used for the campaign of the First Crusade were iter, "journey", and peregrinatio, "pilgrimage".^[3] The terminology of crusading remained largely indistinguishable from that of Christian pilgrimage during the 12th century. This reflected the reality of the first century of crusading, when not all armed pilgrims fought and not all who fought had taken the cross. It was not until the late 12th and early 13th centuries that a more specific "language of crusading" emerged.^[4] Pope Innocent III used the term negotium crucis or "affair of the cross". Sinibaldo Fieschi, the future Pope Innocent IV, used the terms crux transmarina—"the cross overseas"—for crusades in the Outremer (crusader states) against Muslims and crux cismarina—"the cross this side of the sea"—for crusades in Europe against other enemies of the church.^[5] The modern English "crusade" dates to the early 1700s.^[6][1] The term used in modern Arabic, ḥamalāt ṣalībiyya حملات صليبية‎, lit. "campaigns of the cross", is a loan translation of the term "crusade" as used in western historiography.^[7]

The crusades in the Holy Land are traditionally counted as nine distinct campaigns, numbered from the First Crusade of 1095–99 to the Ninth Crusade of 1271–72. This convention was used in 1820 by historian Charles Mills in his History of the Crusades for the Recovery and Possession of the Holy Land. It is often retained for convenience even though it is a somewhat arbitrary system for what some historians now consider to be seven major and numerous lesser campaigns.^[8]

"Saracen]]" was a common term for an Arab Muslim. This was derived from a name used by the later Greeks and Romans for the nomadic peoples of the Syro-Arabian desert who raided the Syrian region of the Roman Empire.^[9] The first English use of "Muslim" is dated to the 17th century.^[9] "Franks" and "Latins" were used by the peoples of the Near East during the crusades for western Europeans, distinguishing them from the Byzantine Christians who were known as "Greeks".^[9][9] Crusader sources used the term "Syrians" to describe Arabic speaking Christians who were members of the Greek Orthodox Church, and "Jacobites" for those who were members of the Syrian Orthodox Church^[13]

Christianity was adopted throughout the Roman Empire in Late Antiquity. The first Christian Roman Emperor, Constantine the Great, founded the great city of Constantinople in 324. In this city the Roman Empire continued until 1453, while the Empire in the west collapsed at the end of the 4th century. The city and the Eastern Roman Empire are more generally known as Byzantium, the name of the older Greek colony it replaced.^[14]

Following the foundation of the Islamic religion by Mohammad in the 7th century, and continuing through the 8th century, Muslim Arabs under the Rashidun and Umayyad Caliphates captured Syria, Egypt, and North Africa from the Roman Empire, Iran from the Sasanian Empire and Iberia from the Visigothic Kingdom.^[15] In 750 a bloody coup brought an end to Umayyad rule to be replaced by the Abbasids and the Islamic state's centre of power moved to Baghdad.^[16]

The initial phase of Turkic migration into the Middle East saw the intersection of Abbasid and Turkic history from the 9th century. One key driver of Middle Eastern state formation for the following thousand years was the use of slave soldiers. Prisoners from the borderlands of Khurasan and Transoxania were transported to central Islamic lands, converted to Islam and given military training. Known as ghulam or mamluks the theory was, that as slaves they would be more loyal to their masters. In practice it took the Turks only a few decades to make the journey from guard, to commander, governor, dynastic founder and eventually king maker. Political cohesion gradually fragmentated. Examples include the Tulanid dynasty in Egypt and Syria (868–905) and the Ikhshidids who followed in Egypt (935–969).^[17]

Muslim Iberia (modern Portugal and Spain) established an independent state in the eighth century, the Sunni-Shia rift intensified over the decades and in 969 North Africa broke away under the Fatamids. These were a Shi'ite faction named after Fatima, the daughter of Mohammad. The Fatimids took control of swathes of the Near East including Jerusalem, Damascus and parts of the Mediterranean coastline. The Fatimids asserted their independence from the Sunni Abbasids and had a rival Shi'ite caliph who they considered the successor to Mohammad.^[18] From the 8th century, the Christians were campaigning to retake Iberia in what has become known as the Reconquista and from 1060 Norman adventurers began the conquest of the Muslim Emirate of Sicily.^[19][20]

The second wave of Turkish migration saw the arrival of the Seljuk Turks in the 10th century.

These were a previously minor ruling clan from Transoxania who had recently converted to Islam and migrated into Iran to seek their fortunes.^[21] In the two decades following their arrival in they conquered Iran, Iraq and the Near East.^[22] The Seljuks and their followers were from the Sunni Islamic tradition which quickly brought them into conflict in Palestine and Syria with the Shi'ite Fatimids.^[18]

The recovery of territory by the Byzantine Empire reached its furthest extent in 1025, through the military successes of Emperor Basil II. Its frontiers stretched as far east as Iran. It controlled Bulgaria as well as much of southern Italy and piracy had been suppressed in the Mediterranean Sea. From this point, the arrival of new enemies on all frontiers placed intolerable strains on the resources of the state. In Italy they were confronted by the Normans; to the north, the Pechenegs, the Serbs and the Cumans, as well as the Seljuks to the east. Emperor Romanos IV Diogenes attempted to confront the Seljuks to suppress sporadic raiding; this led to the 1071 defeat of the Byzantine army at the Battle of Manzikert. Once considered a pivotal event by historians, Manzikert is now regarded as only one step in the expansion of the Great Seljuk Empire into Anatolia.^[23] This situation was probably the cause of instability in the Byzantine hierarchy rather than the result. To maintain order, the Emperors were forced to recruit mercenary armies, sometimes from the very forces that posed the threat. Yet positive signs of the overall health of the Empire at this time have been identified by recent scholarship.^[24]

By the end of the 11th century, the age of Islamic territorial expansion was long gone.^[25] However, fractious frontier conditions between the Christian and Muslim world remained across the Mediterranean Sea.

The territory around Jerusalem had been under Muslim control for more than four centuries.

During this time levels of tolerance, trade, and political relationships between the Muslims and the Christians fluctuated.

Catholic pilgrims had access to sacred sites and Christian residents in Muslim territories were given dhimmi status on payment of a poll tax, legal rights and legal protection. Indigenous Christians were also allowed to maintain existing churches, and marriages between people of different faiths were not uncommon.^[26] The Byzantine Empire and Islamic world were historic centres of wealth, culture and military power. As such, they viewed the West as a backwater that presented little organised threat.^[27]

Historical analysis has demonstrated that the First Crusade had its roots in developments earlier in the 11th century but for Western chroniclers it seems to have been a surprising and unexpected event.

The city of Jerusalem had become increasingly recognised by both laity and clerics as symbolic of penitential devotion. There is evidence that segments of the western nobility were willing to accept a doctrine of papal governance in military matters. The Seljuk hold on the holy city was weak and the Byzantines were open to the opportunity presented by western military aid to fight them. This presented the papacy with a chance to reinforce the principle of papal sovereignty with a display of military power such as that proposed by Pope Gregory VII in 1074 but not followed through.^[28] Warfare was endemic in Western Europe in this period with violence often a part of political discourse. Contemporaries recognised the moral danger which the papacy attempted to deal with by permitting or even encouraging certain types of warfare. The Christian population had a desire for a more effective church which evidenced itself in rioting in Italy and a greater general level of piety. This prompted investment and growth in monasteries across England, France and Germany. Pilgrimage to the Holy Land began in the 4th century but expanded after safer routes through Hungary developed from 1000. It was an increasingly articulate piety within the knighthood and the developing devotional and penitential practises of the aristocracy that created a fertile ground for crusading appeals. Historians, such as Carl Erdmann, once thought the Peace and Truce of God movements restricting warfare between Christians from the 10th century had an impact. The influence is apparent in Pope Urban's speeches. But later scholars, such as Marcus Bull, assert that the movement's effectiveness was limited and it had already died out by the time of the Crusades.^[29] The motivations of the First Crusade also included a "messianism of the poor" inspired by an expected mass ascension into heaven at Jerusalem.^[30]

Before the middle of the 11th-century Gregorian Reform, rival Roman noble families and the Holy Roman Emperor competed to control a papacy that amounted to little more than a localised bishopric. Roman families appointed relatives and protégés as popes,^[31] while Emperor Henry III invaded Rome and replaced two rival candidates with his nominee. The reforming movement coalesced around Pope Leo IX, intent on abolishing simony and clerical marriage and implementing a college of cardinals responsible for electing future popes.^[32] This movement established an assertive, reformist papacy eager to increase its power and influence over secular Europe. A struggle for power developed between Church and state in medieval Europe from around 1075 and continued through the period of the First Crusade. This struggle, now known as the Investiture Controversy,^[33] was primarily about whether the Catholic Church or the Holy Roman Empire held the right to appoint church officials and other clerics. To gather military resources for his conflict with the Emperor, Pope Alexander II developed a system of recruitment via oaths that Pope Gregory VII extended into a network across Europe. This also supported the development of a doctrine of holy war developed from the thinking of 4th-century theologian Augustine of Hippo on the treatment of heresy. Death in a just war came to be seen as martyrdom and warfare itself as a penitential activity.^[34] Gregory's doctrine of papal primacy led to conflict with eastern Christians whose traditional view was that the pope was only one of the five patriarchs of the church alongside the Patriarchates of Antioch, Constantinople, Alexandria and Jerusalem.^[35] In 1054 Leo IX sent a legation to the Patriarch of Constantinople demanded that his supremacy be recognised. The Patriarch responded with an alternative manifesto so the legation excommunicated him. A Synod of the Greek church in turn excommuinicated the legation while condemning the Latin church as heretics in creed and practice. This created an irreparable split known as the East–West Schism. There were now two supposedly universal orthodox Christian realms. Where the principle line of division was between a heathen North and a Christian South, now it was between the Catholic West and an Orthodox East.^[36]

It was the enmity between the Abbasids and Fatamids that prevented any concerted response to Christian invasion.

Power theoretically rested with the respective caliphs in Baghdad and Cairo. In practice executive power was in secular hands: the Sultan in Baghdad and the Vizier in Cairo.^[37] The conquered indigenous Arabs had lived under the Seljuks in relative peace and prosperity. In 1092 that relative stability began to disintegrate 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. 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”.^[38] The confusion meant the Islamic world disregarded the world beyond; this caused it to be vulnerable to, and surprised by, the First Crusade.^[39]

In 1095, Byzantine Emperor Alexios I Komnenos requested military aid from Pope Urban II at the Council of Piacenza, probably a small body of mercenary reinforcements he could direct and control. Alexios had restored the Empire's finances and authority but still faced numerous foreign enemies. Most significant were the migrating Turks, in particular the Seljuks and their followers, who had colonised the sparsely populated areas of Anatolia. Later that year at the Council of Clermont, Urban raised the issue of military support again and preached for a crusade.^[40]

Almost immediately, the French priest Peter the Hermit led thousands of mostly poor Christians out of Europe in what became known as the People's Crusade.^[41] In transit through Germany these crusaders massacred Jewish communities in what became known as the Rhineland massacres. This was part of wide-ranging anti-Jewish activities, extending from limited, spontaneous violence to full-scale military attacks.^[42] Jews were perceived to be as much an enemy as Muslims: they were held responsible for the crucifixion, and were more immediately visible than the distant Muslims. Many people wondered why they should travel thousands of miles to fight non-believers when there were already non-believers closer to home.^[43] The end of the Peoples' Crusade was abrupt. Almost immediately after leaving Byzantine controlled territory on their journey to Nicaea the crusaders were annihilated in a Turkish ambush at the battle of Civetot.^[39]

Conflict with Pope Urban II meant that King Philip I of France and Holy Roman Emperor Henry IV declined to participate in the crusade. But members of the high aristocracy from France, western Germany, the Low Countries, Languedoc and Italy led independent military contingents in loose, fluid arrangements based on bonds of lordship, family, ethnicity and language. Foremost amongst these was the elder statesman, Raymond IV, Count of Toulouse. He was rivalled by the relatively poor but martial Bohemond of Taranto and his nephew Tancred from the Norman community of southern Italy. They were joined by Godfrey of Bouillon and his brother Baldwin and forces from Lorraine, Lotharingia, and Germany. These five princes were pivotal to the campaign, which was also joined by a northern French army led by: Robert Curthose, Count Stephen II of Blois, and Count Robert II of Flanders.^[45] The armies, which may have contained as many as 100,000 people including non-combatants, travelled eastward by land to Byzantium where they were cautiously welcomed by the Emperor.^[46] Alexios persuaded many of the princes to pledge allegiance to him; he also convinced them their first objective should be Nicaea, the capital of the Sultanate of Rum. The over-confident Sultan Kilij Arslan left the city to resolve a territorial dispute, thus enabling its capture after a crusader siege and a Byzantine naval assault. This was a high point in Latin and Greek co-operation and the beginning of crusader attempts to take advantage of disunity in the Muslim world.^[47]

The first experience of Turkish tactics, using lightly armoured mounted archers, occurred when an advanced party led by Bohemond and Robert was ambushed at Dorylaeum. The Normans resisted for hours before the arrival of the main army caused a Turkish withdrawal.^[48] The three-month crusader march to the Muslim city of Antioch was arduous. Numbers were reduced by starvation, thirst and disease, combined with Baldwin's decision to leave with 100 knights and their followers to carve out his own territory in Edessa which became one of the crusader states.^[49] The crusaders besieged Antioch for eight months but lacked the resources to fully invest the city; the residents lacked the means to repel the invaders. Finally, Bohemond persuaded a guard in the city to open a gate. The crusaders entered, massacring the Muslim inhabitants as well as many Christians amongst the Greek Orthodox, Syrian and Armenian communities.^[50]

A force to recapture the city was raised by the Iraqi general Kerbogha. The Byzantines did not march to the assistance of the crusaders because the deserting Stephen of Blois told them the cause was lost. Instead Alexius retreated from Philomelium, where he received Stephen's report, to Constantinople. The Greeks were never truly forgiven for this perceived betrayal and Stephen was branded a coward.^[51] Losing numbers through desertion and starvation in the besieged city, the crusaders attempted to negotiate surrender but were rejected. Bohemond recognised that the only remaining option was open combat and launched a counterattack. Despite superior numbers, Kerbogha's army — which was divided into factions and surprised by the Crusaders commitment and dedication— retreated and abandoned the siege.^[52] The crusaders then delayed for months while they argued over who would have the captured territory. The debate ended when news arrived that the Fatimid Egyptians had taken Jerusalem from the Seljuk Turks, making it imperative to attack before the Egyptians could consolidate their position. Bohemond remained in Antioch, retaining the city, despite his pledge to return it to Byzantine control, while Raymond led the remaining crusader army rapidly south along the coast to Jerusalem.^[53]

An initial attack on the city failed, and the siege became a stalemate, until the arrival of craftsmen and supplies transported by the Genoese to Jaffa tilted the balance. Crusaders constructed two large siege engines; the one commanded by Godfrey breached the walls. For two days the crusaders massacred the inhabitants and pillaged the city. Historians now believe the accounts of the numbers killed have been exaggerated, but this narrative of massacre did much to cement the crusaders' reputation for barbarism.^[54] Godfrey further secured the Frankish position by defeating an Egyptian relief force at Ascalon.^[55] Now, most of the crusaders considered their pilgrimage complete and returned to Europe. When it came to the future governance of the city it was Godfrey who took leadership and the title Defender of the Holy Sepulchre. The original ideas that Jerusalem would become an ecclesiastical domain and the claims of Raymond were discounted in the face of the contingent of troops from Lorraine.^[56] At that point Godfrey was left with a mere 300 knights and 2,000 infantry to defend Palestine. Tancred was the other prince who remained. His ambition was to gain a Crusader state princedom of his own.^[57] When Godfrey died in 1100 the Lorrainers foiled the attempt of Jerusalem's Patriarch, Daimbert to seize power and enabled Godfrey's brother, Baldwin, to take the crown.^[58]

The Islamic world seems to have barely registered the crusade; certainly, there is limited written evidence before 1130.

This may be in part due to a reluctance to relate Muslim failure, but it is more likely to be the result of cultural misunderstanding.

Al-Afdal Shahanshah, the new vizier of Egypt, and the Muslim world mistook the crusaders for the latest in a long line of Byzantine mercenaries, rather than religiously motivated warriors intent on conquest and settlement.^[59] The Muslim world was divided between the Sunnis of Syria and Iraq and the Shi'ite Fatimids of Egypt. Even the Turks remained divided, they had found unity unachievable since the death of Sultan Malik-Shah in 1092, with rival rulers in Damascus and Aleppo.^[60] In Baghdad the Seljuk sultan, Barkiyaruq, vied with an Abbasid caliph, Al-Mustazhir, in a Mesopotamian struggle. This gave the Crusaders a crucial opportunity to consolidate without any pan-Islamic counter-attack.^[61]

The Crusader states were almost constantly at defensive or expansionist war in the early 12th century.

This led to high mortality rates among the nobility as well as a policy of encouraging settlers from the West and Christians from across the Jordan.^[62] Bohemond seized Christian cities in Cilicia, refused to return Antioch and in 1108 organised a Crusade against the Byzantine Empire. The Crusade ended in failure after Alexius starved Bohemond of supplies by cutting his supply lines. The resulting Treaty of Devol, although never implemented, forced Bohemond to acknowledge Alexius feudal as his lord.^[63] Relations between Edessa and Antioch were variable: they fought together in the defeat at Battle of Harran, but the Antiocheans claimed suzerainty and attempted to block the return from his captivity, after the battle, of Count Baldwin—later king of Jerusalem.^[64] This conflict demonstrates the Crusader involvement in Near East politics with Muslims and Christians fighting on both sides. The expansion of Norman Antioch came to an end in 1119 with a major defeat by the Turks at the battle of the Field of Blood.^[65]

Under the papacies of successive popes, smaller groups of crusaders continued to travel to the eastern Mediterranean to fight the Muslims and aid the crusader states.

The third decade of the 12th century saw campaigns by French nobleman Fulk V of Anjou, the Venetians who captured Tyre, and King Conrad III of Germany, as well as the foundation of the Knights Templar, a military order of warrior monks which became international and widely influential. The Templars provided the crusader states with a standing army estimated to have formed half of the states' military forces.^[66]

For the first time, the rise of Imad ad-Din Zengi saw the Crusaders threatened by a Muslim ruler attempting to restore jihad to Near Eastern politics. After his father was executed for treason in the Seljuk succession crisis little is known of his early years. He became Atabeg of Mosul in 1127 and used this to expand his control to Aleppo and then Damascus. In 1144 he conquered Edessa. After a delay of nearly two years preaching began for what subsequently became known as the Second Crusade. Initially, support was sluggish, partly because Pope Eugenius III delegated the preaching. The French Benedictine abbot, Bernard of Clairvaux spread the message that the loss was the result of sinfulness, and redemption was the reward for crusading. Simultaneously, the anti-Semitic element of the crusade preaching of a Cistercian monk called Rudolf initiated further massacres of Jews in the Rhineland.^[67] This formed part of a general increase in crusading activity, including in Iberia and northern Europe.^[68]

Zengi was murdered in uncertain circumstances.

His elder son Saif ad-Din succeeded him as atabeg of Mosul while a younger son Nur ad-Din (died 1174) succeeded him in Aleppo.^[69] For the first time ruling monarchs were campaigning—King Louis VII of France and Conrad III—but the crusade was not a success. Edessa had been destroyed, making its recovery impossible, and the crusade's objectives were unclear. Hostility developed between the French and the Byzantines. The French blamed the Byzantines for defeats suffered against the Seljuks in Anatolia, while the Byzantines laid claims on future territorial gains in northern Syria. As a result, in a decision that historians now criticise, the crusaders attacked the Seljuks of Damascus. This broke a long period of cooperation and coexistence between Jerusalem and Damascus. Bad luck, poor tactics and a feeble five-day siege of Damascus led to internal arguments; the barons of Jerusalem withdrew support and the crusaders retreated before the arrival of a relief army led by Zengi's sons. Morale fell, hostility to the Byzantines grew and distrust developed between the newly arrived crusaders and those that had made the region their home after the earlier crusades.^[70]

After the conquest of Ascalon in 1153 opened a strategic road south from Palestine, Jerusalem demonstrated an increasing interest in expanding into Egyptian territory.

In 1160 King Baldwin III planned an invasion that was only prevented by Egypt paying a tribute of 160,000 gold dinars.^[71] In 1163 Shawar—who had been deposed as vizier in an outbreak of systemic and murderous political intrigue—arrived in Damascus to meet with Nur ad-Din. His aim was to gain the political and military support necessary to regain his position. Nur ad-Din prevaricated before responding when it became clear that, otherwise, the crusaders might gain a strategic foothold on the Nile. Some historians consider this decision a visionary attempt to surround the crusaders.^[72] Nur ad-Din sent his Kurdish general, Shirkuh, who stormed Egypt and restored Shawar. However, Shawar asserted his independence and allied with Baldwin's brother and successor King Amalric. When Amalric broke the alliance in a ferocious attack, Shawar again requested military support from Syria. Shirkuh was sent by Nur ad-Din for a second time, accompanied by his nephew, Yusuf ibn Ayyub, who became known by his honorific 'Salah al-Din' ('the goodness of faith'), which has been westernised as Saladin. Amalric retreated. Saladin captured Shawar on his way to peace negotiations and he was quickly executed. Shirkuh was appointed vizier. When he died two months later, Saladin successfully intrigued to be appointed vizier.^[73] Nur ad-Din died in 1174, the first Muslim to unite Aleppo and Damascus in the crusading era. Assuming control after the death of his overlord Nur al-Din, Saladin had the strategic choice of establishing Egypt as an autonomous power or attempting to become the pre-eminent Muslim in the eastern Mediterranean; he chose the latter.^[74]

As Nur al-Din's territories became fragmented after his death, Saladin legitimised his ascent by positioning himself as a defender of Sunni Islam subservient to both the Caliph of Baghdad and to Nur al-Din's 11-year-old son and successor, As-Salih Ismail al-Malik.^[75] While claiming to be the young prince's regent until the boy died seven years later, he seized Damascus and much of Syria but failed to take Aleppo.^[76] After building a defensive force to resist a planned attack by the Kingdom of Jerusalem that never materialised, his first contest with the Latin Christians was not a success. His overconfidence and tactical errors led to defeat at the Battle of Montgisard.^[77] Despite this setback, Saladin established a domain stretching from the Nile to the Euphrates through a decade of politics, coercion and low-level military action.^[78] After a life-threatening illness early in 1186, he determined to make good on his propaganda as the champion of Islam, embarking on heightened campaigning against the Latin Christians.^[79] King Guy responded by raising the largest army that Jerusalem had ever put into the field. Saladin lured the force into inhospitable terrain without water supplies, surrounded the Latins with a superior force, and routed them at the Battle of Hattin. Guy was amongst the Christian nobles taken prisoner, but he was later released. Saladin offered the Christians the option of remaining in peace under Islamic rule or taking advantage of 40 days' grace to leave. As a result of his victory, much of Palestine quickly fell to Saladin, including—after a short five-day siege—Jerusalem.^[80] According to Benedict of Peterborough, Pope Urban III died of deep sadness on 19 October 1187 after hearing of the defeat.^[81]

Urban III's successor as pope, Gregory VIII, issued a papal bull titled Audita tremendi that proposed what became known as the Third Crusade to recapture Jerusalem. In August 1189, the freed King Guy attempted to recover Acre from Saladin by surrounding the strategic city, only for his own forces to be besieged in turn.^[82][83] Both armies could be supplied by sea, so a long stalemate commenced. The crusaders became so deprived at times they are thought to have resorted to cannibalism.^[84] Travelling overland to join the crusade, Holy Roman Emperor Frederick I drowned in the Saleph River; few of his men reached their destination.^[85] Richard the Lionheart, King of England, travelled by sea; his sister and his fiancée travelled separately. In response to their capture by the Cypriot ruler, Isaac Komnenos, Richard conquered the island in 1191.^[86] Philip II of France was the first king to arrive at the siege of Acre; Richard arrived on 8 June 1191.^[82] The arrival of the French and Angevin forces turned the tide in the conflict, and the Muslim garrison of Acre finally surrendered on 12 July. Philip considered his vow fulfilled and returned to France to deal with domestic matters, leaving most of his forces behind. But Richard travelled south along the Mediterranean coast, defeated the Muslims near Arsuf, and recaptured the port city of Jaffa. He twice advanced to within a day's march of Jerusalem. Richard judged that—while Saladin had a mustered army—he himself lacked the resources to successfully capture the city or defend it in the unlikely event of a successful assault. This marked the end of Richard's crusading career and was a calamitous blow to Frankish morale.^[87] A three-year truce was negotiated that allowed Catholics unfettered access to Jerusalem.^[88] Politics in England forced Richard's departure, never to return; Saladin died in March 1193.^[82] Holy Roman Emperor Henry VI initiated the German Crusade to fulfil the promises to undertake a crusade to the Holy Land made by his father Frederick. Led by Conrad, Archbishop of Mainz, the army captured the cities of Sidon and Beirut. In 1197 Henry died and most of the crusaders returned to Germany to protect their holdings and take part in the election of his successor as Emperor.^[89]

Pope Innocent III announced a new Crusade on his election in 1198.^[90] Crusaders arrived in insufficient numbers to pay the Venetians for the fleet for which they had contracted.

Enrico Dandolo, the Doge of Venice, diverted the crusaders to seize the Christian city of Zara for supplies and to compensate for the failure to fulfil the treaty. Innocent III's role was ambivalent. He only condemned the attack when the siege started. He withdrew his legate to disassociate from the attack but seems to have accepted it as inevitable. Historians question whether for him, the papal desire to salvage the crusade may have outweighed the moral consideration of shedding Christian blood.^[91]

Innocent did excommunicate the Venetians who continued to plot to further their aggressive territorial objectives.

They were joined by King Philip of Swabia, who intended to use the Crusade to restore his exiled nephew, Alexios IV Angelos, to the throne of Byzantium. The latter would require the overthrow of Alexios III Angelos, the uncle of Alexios IV.^[92] It was agreed the crusade would attack Constantinople supporting Venice's objectives. The plan was that when these were achieved, Alexios IV would provide the crusade passage to the Holy Land or Egypt.^[93]

Alexios III fled.

The crusaders initially took Constantinople easily, but not the wider Byzantine Empire. But Alexios IV Angelos was unable or unwilling to fulfil his commitments and the original purpose of the campaign was defeated by his murder in a violent anti-Latin Byzantine revolt. In response the crusaders sacked the city, which involved three days of pillaging churches and killing many Greek Orthodox Christians. The continuation of the crusade was now impossible because many crusaders now lacked the desire for further campaigning and the crusade no longer had the necessary Byzantine logistical support. The result was that the Fourth Crusade never came within 1,000 miles of its objective of Jerusalem.^[94] Instead it increased Latin territory in the East including Constantinople, demonstrated that poor organisation could wreck an expedition and set a precedent that crusades could legitimately attack not only Muslims but other enemies of the Papacy.^[95]

The 13th century saw a new military threat to the Christian and Islamic worlds.

The Mongols swept west from Mongolia through southern Russia, Poland and Hungary while also defeating the Seljuks and threatening the crusader states.^[96] Separately, Europe saw popular outbursts of ecstatic piety in support of the crusades, such as that resulting in the Children's Crusade in 1212. Large groups of young adults and children spontaneously gathered, believing their innocence would enable success where their elders had failed. Few, if any at all, journeyed to the eastern Mediterranean. Although little reliable evidence survives for these events, they provide an indication of how hearts and minds could be engaged for the cause.^[97][98]

Saladin's brother Al-Adil disinherited Saladin's sons from the Ayyubid succession. He lacked the Islamic moral authority of his brother required to unite the Muslim world. The result was he left the kingdom of Jerusalem in peace between 1194 and 1217 prompting a revival of the kingdom. Innocent III's Fourth Lateran Council in 1213 called for another Crusade. In the papal bull Quia maior he did much to codify existing practices in preaching, recruitment and financing the crusades. The plenary indulgence was defined as forgiveness of the sins confessed to a priest for those who fought in, or even provided funding for crusades. Geoffrey Chaucer's The Pardoner's Tale may demonstrate a cynical view of vow commutation but it was a pragmatic approach that led to more people taking the cross and raising more money in the following century than in the previous hundred years.^[99] The lack of immediate threat and the wait for the expiration of a number of treaties meant that crusading did not resume until 1217, after Innocent's death.^[100]

In what is categorised as the Fifth Crusade a force—primarily raised from Hungary, Germany, Flanders—led by King Andrew II of Hungary and Leopold VI, Duke of Austria achieved little. Leopold and John of Brienne, the King of Jerusalem and later Latin Emperor of Constantinople, besieged and captured Damietta, but an army advancing into Egypt was compelled to surrender.^[101] Damietta was returned, and an eight-year truce agreed.^[102]

Holy Roman Emperor Frederick II was excommunicated for breaking a treaty obligation with the pope and failing to join the crusade. But after his marriage to Isabella II of Jerusalem, John of Brienne's daughter and heir, he had a claim to the kingdom of Jerusalem prompting him to journey to Acre in 1228. Frederick was culturally the Christian monarch most empathetic to the Muslim world, having grown up in Sicily, with a Muslim bodyguard and even a harem. His great diplomatic skills meant the Sixth Crusade was largely a negotiation supported by force.^[103] A peace treaty was agreed upon giving Latin Christians most of Jerusalem and a strip of territory that linked the city to Acre while the Muslims controlled their sacred areas. In return, an alliance was made with Al-Kamil, Sultan of Egypt, against all of his enemies of whatever religion. The treaty, and suspicions about Frederick's ambitions in the region, made him unpopular, and he was forced to return to his domains when they were attacked by Pope Gregory IX.^[104]

Attention given to the conflict between Holy Roman Empire and the papacy often meant that the responsibility for the prioritisation of campaigns in the Crusader states fell to secular, rather than papal, leadership.

What is sometimes known as the Barons' Crusade was first led by Count Theobald I of Navarre and when he returned to his lands, by the king of England's brother, the newly arrived Richard of Cornwall. Sultan al-Kamil had died and his family were battling for the succession in Egypt and Syria. This allowed the crusaders to follow Frederick's tactics of combining forceful diplomacy with playing rival factions off against each other.^[105] The sparsely populated Jerusalem was in Christian hands and the territorial reach was that of the Kingdom before the disaster at Hattin in 1187. This brief renaissance for Frankish Jerusalem was illusory. The Jerusalem nobility rejected the succession of the Emperor's son to the kingdom's throne. As a result, the kingdom could no longer rely on the resources of the Holy Roman Empire and was left dependent on Ayyubid division, the crusading orders and other western aid for survival.^[106]

The Mongols displaced a central Turkish Asian people, the Khwarazmian, providing Al-Kamil's son As-Salah with useful allies.^[107] The Khwarazmians savagely captured Jerusalem, pursuing the Christian refugees. Only 300 reached safety at Ramla. A combined Egyptian Khwarazmian then defeated an army of Christians and Syrians at the battle of La Forbie. This was the last occasion the Crusader State nobility had the resources to put an army in the field. The Patriarch of Jerusalem put the total loses at 16,000; only 36 out of 348 templars, 26 out of 351 Hospitallers and 3 out 0f 400 Teutonic knights escaped alive.^[108] When Innocent IV wrote to the Mongols to question what right they had to attack peaceful Christians in Russia, Poland and Hungary they replied by demanding his total submission to their authority^[109]

Thirteenth-century politics in the eastern Mediterranean was complex, with numerous powerful and interested parties.

The French were led by the very devout Louis IX, king of France, and his ambitiously expansionist brother Charles. Communication with th Mongols was hindered by the enormous distances involved. Louis sent an embassy to the Mongols in Iran in 1249 seeking an Franco-Mongol alliance.^[110] When the reply found him in Palestine in 1251 it was again only a demand for tribute. Louis organised a new crusade, called the Seventh Crusade, to attack Egypt, arriving in 1249.^[111] He was defeated at Mansura and captured as he retreated to Damietta. Another ten-year truce was agreed. Louis and his nobles were ransomed while the other prisoners were given a choice between conversion to Islam or beheading.^[112] He remained in Syria until 1254 to consolidate the crusader states.^[113] A brutal power struggle developed in Egypt between various Mamluk leaders and the remaining weak Ayyubid rulers. The Mamluks were slave soldiers that had been used by Muslim rulers for centuries. Most of them were Turks from the Eurasian Steppe or Christians from Anatolia; kidnapped as boys, converted to Islam and given military training.^[114][115] The threat presented by an invasion by the Mongols led to Qutuz seizing the sultanate in 1259 and uniting with another faction led by Baibars to defeat the Mongols at Ain Jalut. The Mamluks then quickly gained control of Damascus and Aleppo before Qutuz was assassinated, most probably by Baibers.^[116]

Between 1265 and 1271, Sultan Baibars drove the Franks to a few small coastal outposts.^[117] Baibars had three key objectives: to prevent an alliance between the Latins and the Mongols, to cause dissension among the Mongols (particularly between the Golden Horde and the Persian Ilkhanate), and to maintain access to a supply of slave recruits from the Russian steppes. He supported King Manfred of Sicily's failed resistance to the attack of Charles and the papacy. Dissention in the crusader states led to conflicts such as the War of Saint Sabas. Venice drove the Genoese from Acre to Tyre where they continued to trade with Baibars' Egypt. Indeed, Baibars negotiated free passage for the Genoese with Michael VIII Palaiologos, Emperor of Nicaea, the newly restored ruler of Constantinople.^[118] In 1270 Charles turned his brother King Louis IX's crusade, known as the Eighth, to his own advantage by persuading him to attack his rebel Arab vassals in Tunis. The crusader army was devastated by disease, and Louis himself died at Tunis on 25 August. The fleet returned to France. Prince Edward, the future king of England, and a small retinue arrived too late for the conflict but continued to the Holy Land in what is known as the Ninth Crusade. Edward survived an assassination attempt, negotiated a ten-year truce, and then returned to manage his affairs in England. This ended the last significant crusading effort in the eastern Mediterranean.^[119]

The 1281 election of a French pope, Martin IV, brought the full power of the papacy into line behind Charles. He prepared to launch a crusade against Constantinople but, in what became known as the Sicilian Vespers, an uprising fomented by the Byzantine Emperor Michael VIII proclaimed Peter III of Aragon as king of Sicily depriving Charles of the resources of the island. In response, Martin excommunicated Peter and called for an Aragonese Crusade, which was unsuccessful. In 1285 Charles died, ending a period when he and his brother and later saint, Louis, had viewed themselves as God's instruments to uphold the papacy. He had spent his life in the attempt to amass a Mediterranean empire.^[120]

The causes of the decline in crusading and the failure of the crusader states are multi-faceted.

Historians have attempted to explain this in terms of Muslim reunification and jihadi enthusiasm but Thomas Asbridge, amongst others, considers this too simplistic. Muslim unity was sporadic and the desire for jihad ephemeral. The nature of crusades was unsuited to the conquest and defence of the Holy Land. Crusaders were on a personal pilgrimage and usually returned when it was completed. Although the philosophy of crusading changed over time, the crusades continued to be conducted by short-lived armies led by independently minded potentates, rather than with centralised leadership. What the crusader states needed were large standing armies. Religious fervour enabled significant feats of military endeavour but proved difficult to direct and control. Succession disputes and dynastic rivalries in Europe, failed harvests and heretical outbreaks, all contributed to reducing Latin Europe's concerns for Jerusalem. Ultimately, even though the fighting was also at the edge of the Islamic world, the huge distances made the mounting of crusades and the maintenance of communications insurmountably difficult. It enabled the Islamic world, under the charismatic leadership of Zengi, Nur al-Din, Saladin, the ruthless Baibars and others, to use the logistical advantages of proximity to victorious effect.^[121]

The mainland Crusader states were finally extinguished with the fall of Tripoli in 1289 and Acre in 1291. It is reported that many Latin Christians evacuated to Cyprus by boat, were killed or enslaved. Despite this, Ottoman census records of Byzantine churches show that most parishes in the former Crusader states survived at least until 16th-century and remained Christian.^[122][123]

The success of the First Crusade led to further and multifaceted crusading in the Middle Ages.

The Western Europeans developed a different, overtly spiritual, perception of the reconquest of the Iberian Peninsula. Other conflicts began to be seen as crusades with crusading privileges and legal frameworks applied. These conflicts outside the Holy Land included the territorial wars in the Baltic, the popes' wars against their political enemies in Italy and, after the Fourth Crusade, the defence of the Latin Empire of Constantinople.^[124]

At the time of the First Crusade, Spain had the largest population of Latin Christians living under Muslim rule.

The period of Islamic conquest was over by c. 900, and in 1031 the collapse of the Caliphate of Córdoba created the political conditions that would make the Reconquista possible. The Christian powers in Spain had no common identity or shared history based on tribe or ethnicity. As a result, the Kingdom of León, the Kingdom of Navarre and Catalonia united and divided several times in the 11th and 12th centuries. Although small, all had developed a military aristocracy and technique.^[125] By the time of the Second Crusade three kingdoms had become powerful enough to embark on the conquest of Islamic territory—Castile and León, Aragon and Catalonia and Portugal. A consensus has emerged among modern historians against the view of a generation of Spanish scholars who believed that a Spanish religious and national victory over Islam was inevitable.^[126] In 1123 Pope Calixtus II issued a bull creating an equivalence between the Reconquista and crusading in the east against Muslims. It was during the period of the Second Crusade that the Reconquista was placed within the context of crusading and Pope Eugenius III named Iberia as an objective. The Genoese provided logistic support, a mixed band of crusaders captured Lisbon, which was one of the few Christian victories of the Second Crusade, and Bernard of Clairvaux preached for the campaign in the same terms as he did against the Wends.^[127]

In 1212, the Battle of Las Navas de Tolosa was won by the Spanish with the support of 70,000 foreign combatants responding to a crusade preached by Innocent III. Many of the foreigners deserted because of the tolerance the Spanish demonstrated for the defeated Muslims. For the Spanish, the Reconquista was a war of domination rather than a war of extinction.^[128] This contrasted with the treatment of the Christians formerly living under Muslim rule, the Mozarabs. The Roman Rite was relentlessly imposed, and the native Christians were absorbed into the mainstream Roman church by the Cistercians, Cluniac clerical appointments and the military orders.^[123] The Reconquista continued to attract crusaders and crusader privileges.^[129] Al-Andalus, Islamic Spain, was completely suppressed in 1492 when the Emirate of Granada surrendered. At this point the remaining Muslim and Jewish inhabitants were expelled from the peninsula.^[130]

At the Third Council of the Lateran in 1179, Pope Innocent III set a precedent relevant to those crusades that were and are considered as political. In this he encouraged those who suppressed sects considered heretical by the offering of indulgences. One early 13th-century example was the twenty years of campaigning—primarily by French nobility— to suppress a heretical sect called the Cathars in southern France. This is now known as the Albigensian Crusade and is named after the city of Albi, one of the main centres of Catharism. The thirty-year delay in instigating the crusade illustrates a lack of priority given to the campaign in comparison with the more immediate response in crusading rhetoric regarding the papal territorial conflicts in Italy.^[131] The Albigensian Crusade taught the papacy that it was in fact far easier to attack those who tolerated heresy rather than to identify and eradicate the heresy itself. Pressure was exerted on the Commune of Milan because of allegations that the city tolerated Catharism. In Languedoc, feudal lords who failed in its suppression had their lands confiscated and titles forfeited. The historian Norman Housley notes the strong political undertones and connection between heterodoxy and anti-papalism. The pope and the Inquisition would claim that anyone not with them was against them and label opponents as Cathars without requiring evidence. Indulgences were offered to anti-heretical groups such as the Militia of Jesus Christ and the Society of the Blessed Virgin in Milan.^[132]

In 1147, the papacy began to describe the wars waged by Scandinavian and German Christians against the pagans in the Baltic coastal region as crusades.

Bernard of Clairvaux persuaded Pope Eugenius III that the conflict with the Wends was a holy war analogous to the Reconquista, even though the Germans were more motivated by wars of territorial conquest than events in the east.

This Wendish Crusade saw Saxons, Danes, and Poles begin to forcibly convert the neighbouring tribes of Polabian Slavs or "Wends".^[133] This, and further campaigns against Estonian and Finnish pagans were understood in religious terms by contemporaries as a struggle against paganism. The theoretical justification, however, was weak without the argument that the crusaders were fighting to reclaim Christian territory.^[133]

Military orders played a controversial role in the Baltic, most notably the Teutonic Knights who were founded in Palestine after the Siege of Acre in the 1190s and modelled on the Templars. A precedent for the knights had already been set by the Livonian Brothers of the Sword and the Order of Dobrzyń who were founded to defend Riga and German commercial interests. The Teutonic Knights' strong links to German imperium diverted efforts from the Holy Land to Prussia and Livonia. The order conducted harsh and brutal suppression of the local populations, including Orthodox Christians. In this way Latin control was extended 300 miles (480 kilometres) to the east in the 13th century.^[134] Historian Robert Bartlett defines the conquest and organisation of power in the Baltic as part of a general movement for 'the expansion of Latin Christendom'. It was made possible by the crusading ideology placing the full machinery of the Church behind superior military technology. It enabled the recruitment of troops via preaching, the offer of spiritual rewards for combatants and the administrative machinery to establish government in the conquered territories.^[135]

Crusades were launched during the 14th and 15th centuries to counter further Ottoman expansion in the Balkans. The Ottomans had conquered most of the Balkans and reduced Byzantine influence to the area immediately surrounding Constantinople after their victory at the Battle of Kosovo in 1389. Pope Boniface IX proclaimed a new Crusade of Nicopolis to recover the city from the Ottomans, that ended in 1396 with a comprehensive defeat in the Battle of Nicopolis and left Bulgaria in Muslim hands for 500 years.^[136] As the Ottomans pressed westward, Sultan Murad II destroyed the last papal-funded crusade at Varna on the Black Sea in 1444. Four years later, he crushed the last Hungarian expedition.^[137] After the fall of Constantinople the crusading response was largely symbolic even when there was a genuine plan, such as Duke Phillip of Burgundy's promotion of a crusade that never materialised at the Feast of the Pheasant.^[138]

Venice was the only polity to continue to pose a significant threat to the Ottomans in the Mediterranean, but it pursued the "crusade" mostly for its commercial interests, leading to the protracted Ottoman–Venetian Wars, which continued, with interruptions, until 1718. The end of crusading in terms of at least nominal efforts by Catholic Europe against Muslim incursions, came in the 16th century, when the Franco-Imperial wars assumed continental proportions. King Francis I of France sought allies from all quarters, including from German Protestant princes and Muslims. Amongst these, he entered into one of the capitulations of the Ottoman Empire with Ottoman Sultan Suleiman the Magnificent while making common cause with Hayreddin Barbarossa, an Ottoman admiral, and the Sultan's North African vassals.^[139]

After the First Crusade's capture of Jerusalem and victory at Ascalon most crusaders considered their personal pilgrimage complete and returned to Europe.

Godfrey of Bouillon found himself left with only 300 knights and 2,000 infantry to defend the territory won in the eastern Mediterranean.^[57] At this point the Franks held Jerusalem and two great Syrian cities—Antioch and Edessa—but not the surrounding country.

Jerusalem remained economically underdeveloped despite the advantages of being the centre of administration of church and state and benefiting from streams of pilgrims.^[140] Modern research based on historical geography techniques indicate that Muslims and indigenous Christian populations were less integrated than previously thought.

Palestinian Christians lived around Jerusalem and in an arc stretching from Jericho and the Jordan to Hebron in the south. Central areas appear to have had a Muslim majority population from the 6th century, when the Samarian communities were destroyed. These communities are now thought to be of nearly equal size, perhaps even in a 50:50 proportion.^[123]

The Frankish population of the Kingdom of Jerusalem became concentrated in three major cities.

By the 13th century the population of Tyre probably exceeded 60,000, then came Acre and the capital itself was the smallest of the three with a population somewhere between 20,000 and 30,000.^[141] At the zenith of the crusader states, the total Latin population of the region reached around 250,000 with the kingdom of Jerusalem amounting to about 120,000 and the total combined numbers in Tripoli, Antioch and Edessa being broadly similar.^[142] My way of context, Josiah Russell estimates the population of Islamic territory in the region as 12.5 million in 1000—Anatolia 8m, Syria 2m, Eqypt 1.5m and Nprth Arica 1m— with the European areas that provided crusaders having a population of 23.7 million. He estimates by 1200 that these figures had risen to 35.6 million in Islamic territory—Anatolia 7 million, Syria 2.7m, Egypt 2.5m and North Africa 1.5 million— while the crusaders home countries population was 35.6 million.^[143]

The new territories were based on shared language, family or feudal ties and the settlers' regions of origin.

The Principality of Antioch, founded in 1098 and ruled by Bohemond, became Norman in character and custom. The Kingdom of Jerusalem, founded in 1099, followed the traditions of northern France. The County of Tripoli, founded in 1104 (although the city of Tripoli itself remained in Muslim control until 1109) by Raymond de Saint-Gilles became Provençal. The County of Edessa, founded in 1098, differed in that although it was ruled by men from northern France, relatives of the counts of Boulogne and lords of Courtenay, its largely Armenian and Jacobite native nobility was preserved.^[144][145] These states were the first examples of "Europe overseas". They are generally known by historians as Outremer, from the French outre-mer ("overseas" in English).^[9][147]

The "Law of Conquest" supported the seizure of land and property by impecunious crusaders from the indigenous population, enabling poor men to become rich and part of the nobility. However some historians, like Andrew Jotischky, question the model once proposed, where the primary motivation was understood in sociological and economic rather than spiritual terms.^[148] The Franks did not distinguish on grounds of religion; the basic division in society was between Frank and non-Frank, and not between Christian and Muslim. The new Frankish rulers did not expel the native population but adopted strict segregation and at no point attempted to integrate it by way of religious conversion. In this way the crusaders created a colonial nobility that perpetuated itself through an incessant flow of religious pilgrims and settlers keen to take economic advantage.^[144]

The key differentiator in status and economic position in the crusader states was between urban and rural dwellers.

There was no Frankish peasantry; this was a role fulfilled by the native peoples.

The Franks imposed their own feudal culture on agricultural production which made little difference to the conditions of the rural population.

However, the Muslim poll tax on non-Muslims was reversed.

This enabled the feudal Lords to raise punitive levels of revenue from indigenous peoples, whether Muslim, Jewish or Christian.

Very few Muslims lived in urban areas except those in servitude, although indigenous Christians could gain legal status and acquire wealth through commerce and industry in towns.^[149]

Largely based in the ports of Acre and Tyre, Italian, Provençal and Spanish communes had distinct cultural characteristics and exerted significant political power.

Separate from the Frankish nobles or burgesses, the communes were autonomous political entities closely linked to their countries of origin.

This gave the inhabitants the ability to monopolise foreign trade and almost all banking and shipping in the crusader states.

Every opportunity to extend trade privileges was taken.

One example saw the Venetians receiving one-third of Tyre, its territories and exemption from all taxes, after Venice participated in the successful 1124 siege of the city. Despite all efforts, the two ports were unable to replace Alexandria and Constantinople as the primary centres of commerce in the region.^[150] Instead, the communes competed with the king of Jerusalem and each other to maintain economic advantage. Power derived from the support of the communards' native cities rather than their number, which never reached more than hundreds. Thus, by the middle of the 13th century, the rulers of the communes were barely required to recognise the authority of the crusaders and divided Acre into several fortified miniature republics.^[151]

Records preserved by John of Ibelin indicate that the military force of the kingdom of Jerusalem was based on a feudal host of about 647 to 675 knights in 1170. Each feudatory would also provide his own armed retainers. This force would be augmented by mercenary serjants and John records 5,025 of these. In times of emergency, the king could also call upon a general muster of the population. Historian Joshua Prawer estimates that the military orders could match the fighting strength of the king's army. This means the total military strength of the kingdom can be estimated at 1,200 knights and 10,000 serjants. This indicates further territorial gains were possible, but these were likely to be nothing more than ephemeral because of a lack of the required numbers to maintain military domination. This demographic lack of numbers was also a problem defensively. Putting an army into the field required draining every crusader castle and city of all able-bodied fighting men. In the case of a defeat such as the battle of Hattin, there remained no one to resist the invaders. Muslim armies were incohesive and seldom campaigned beyond a period between sowing and harvest. As a result, the crusaders adopted delaying tactics when faced with a superior invading Muslim force. They would avoid direct confrontation, instead retreating to strongholds and waiting for the Muslim army to disperse. It took generations before the Muslims recognised that the destruction of the walled cities and castles would end crusader rule. This strategic change forced the crusaders away from the tactic of gaining and holding territory, including Jerusalem. Instead the aim was to attack and destroy Egypt. By removing this constant regional challenge, the Crusaders hoped to gain the necessary time to improve the kingdom's demographic weakness.^[152]

The conquest of Christian Constantinople by the Fourth Crusade created a significant increase in the Frankish crusader presence in the eastern Mediterranean.

Those crusaders that remained established control over the city, Thrace, Greece, the extreme north west of Anatolia as well as the Ionian and Aegean Islands. A council of six Venetians and six Franks selected Count Baldwin of Flanders as a new Latin Emperor.^[135] This established a Latin Empire in the east and partitioned the Byzantine territory. Venice gained a maritime domain including Istria, Dalmatia, Albania, Negroponte, the Kingdom of the Morea, the Aegean islands of the Duchy of the Archipelago, and the islands of Crete, the Kingdom of Candia and Cyprus. This endured long standing conflict with the Ottoman Empire until the final possessions were lost in the Seventh Ottoman–Venetian War in the 18th century. The Latin emperor controlled one-fourth of the Byzantine territory, Venice three-eighths (including three-eighths of the city of Constantinople), and the remainder was divided among the other leaders of the crusade. This period of Greek history is known as the Frankokratia or Latinokratia ("Frankish or Latin rule") and designates a period when Catholic western European nobles, primarily from France and Italy, ruled over the Orthodox Byzantine Greeks on former Byzantine territory.^[153][2] In the long run, the sole beneficiary was Venice.^[154]

The crusaders' propensity to follow the customs of their Western European homelands meant that there were very few innovations developed from the culture in the crusader states.

Three notable exceptions to this are the military orders, warfare and fortifications.^[155] The Knights Hospitaller, formally the Order of Knights of the Hospital of Saint John of Jerusalem, were founded in Jerusalem before the First Crusade but added a martial element to their ongoing medical functions to become a much larger military order.^[156] In this way the knighthood entered the previously monastic and ecclesiastical sphere.^[157]

Military orders like the Knights Hospitaller and Knights Templar provided Latin Christendom's first professional armies in support of the Kingdom of Jerusalem and the other crusader states.

The Templars, formally the Poor Fellow-Soldiers of Christ and the Temple of Solomon, and their Temple of Solomon were founded around 1119 by a small band of knights who dedicated themselves to protecting pilgrims en route to Jerusalem.^[91] The Hospitallers and the Templars became supranational organisations as papal support led to rich donations of land and revenue across Europe. This, in turn, led to a steady flow of new recruits and the wealth to maintain multiple fortifications in the crusader states. In time, they developed into autonomous powers in the region.^[159] After the fall of Acre the Hospitallers first relocated to Cyprus, then conquered and ruled Rhodes (1309–1522) and Malta (1530–1798), and continue in existence to the present-day. King Philip IV of France probably had financial and political reasons to oppose the Knights Templar, which led to him exerting pressure on Pope Clement V. The pope responded in 1312, with a series of papal bulls including Vox in excelso and Ad providam that dissolved the order on the alleged and probably false grounds of sodomy, magic and heresy.^[160]

According to Joshua Prawer no major European poet, theologian, scholar or historian settled in the crusader states. Some went on pilgrimage, and this is reflected in new imagery and ideas in the important area of western poetry. Although they did not migrate East themselves, their output often encouraged others to journey on pilgrimage to the east.^[161]

Historians consider military architecture—demonstrating a synthesis of the European, Byzantine and Muslim traditions—the most original and impressive artistic achievement of the crusades.

Castles were a tangible symbol of the dominance of a Latin Christian minority over a largely hostile majority population.

They also acted as centres of administration.^[162] Modern historiography rejects the 19th-century consensus that Westerners learnt the basis of military architecture from the Near East, as Europe had already experienced rapid growth in defensive technology before the First Crusade.

Direct contact with Arab fortifications originally constructed by the Byzantines did influence developments in the east.

But the lack of documentary evidence means that it remains difficult to differentiate between the importance of this design culture and the constraints of situation, which led to the inclusion of oriental design features such as large water reservoirs and the exclusion of occidental features like moats.^[163]

Typically, early church design was in the French Romanesque style. This can be seen in the 12th-century rebuilding of The Church of the Holy Sepulchre. It retained some of the Byzantine details, but new arches and chapels were built to northern French, Aquitanian and Provençal patterns. There is little trace of any surviving indigenous influence in sculpture, although in the Holy Sepulchre the column capitals of the south facade follow classical Syrian patterns.^[164]

In contrast to architecture and sculpture, it is in the area of visual culture that the assimilated nature of the society was demonstrated.

Throughout the 12th and 13th centuries the influence of indigenous artists was demonstrated in the decoration of shrines, painting and the production of manuscripts.

In addition, Frankish practitioners borrowed methods from the Byzantines and indigenous artists and iconographical practice.

Monumental and panel painting, mosaics and illuminations in manuscripts adopted an indigenous style leading to a cultural synthesis illustrated by the Church of the Nativity. Wall mosaics were unknown in the west but in widespread use in the crusader states. Whether this was by indigenous craftsmen or learnt by Frankish ones is unknown, but a distinctive original artistic style evolved.^[165]

Manuscripts were produced and illustrated in workshops housing Italian, French, English and local craftsmen leading to a cross-fertilisation of ideas and techniques.

An example of this is the Melisende Psalter, created by several hands in a workshop attached to the Holy Sepulchre. This style could have either reflected or influenced the taste of patrons of the arts. But what is seen is an increase in stylised Byzantine-influenced content. This even extended to the production of icons, unknown at the time to the Franks, sometimes in a Frankish style and even of western saints. This is seen as the origin of Italian panel painting.^[166] While it is difficult to track illumination of manuscripts and castle design back to their sources textual sources are simpler. The translations made in Antioch are notable, but they are considered of secondary importance to the works emanating from Muslim Spain and from the hybrid culture of Sicily.^[167]

The Kingdom of Jerusalem was the first experiment in European colonialism, setting up a "Europe Overseas" or the Outremer. The raising, transportation, and supply of large armies led to flourishing trade between Europe and the Outremer. The Italian city-states of Genoa and Venice flourished, planting profitable trading colonies in the eastern Mediterranean.^[168] The crusades consolidated the papal leadership of the Latin Church, reinforcing the link between Western Christendom, feudalism, and militarism and increased the tolerance of the clergy for violence.^[92] Muslim libraries contained classical Greek and Roman texts that allowed Europe to rediscover pre-Christian philosophy, science and medicine.^[169] The growth of the system of indulgences became a catalyst for the Reformation in the early 16th century.^[166] The crusades also had a role in the formation and institutionalisation of the military and the Dominican orders as well as of the Medieval Inquisition.^[171]

The behaviour of the crusaders in the eastern Mediterranean area appalled the Greeks and Muslims.

It created a lasting barrier between the Latin world and both the Islamic and Orthodox religions.

It became an obstacle to the reunification of the Christian church and fostered a perception of Westerners as defeated aggressors.^[92] Many historians argue that the interaction between the western Christian and Islamic cultures played a significant, ultimately positive, part in the development of European civilisation and the Renaissance.^[172] Relations between Europeans and the Islamic world stretched across the entire length of the Mediterranean Sea. This led to an improved perception of Islamic culture in the West, but also makes it difficult for historians to identify the specific sources of cultural cross-fertilisation.^[167]

Historical parallelism and the tradition of drawing inspiration from the Middle Ages have become keystones of political Islam encouraging ideas of a modern jihad and long struggle. Secular Arab nationalism highlights the role of western imperialism. Egyptian President Gamal Abdel Nasser likened himself to Saladin and imperialism to the crusades. In his History of the Crusades Said Ashour emphasised the similarity between the modern and medieval situation facing Muslims and the need to study the crusades in depth. Sayyid Qutb declared there was an international crusader conspiracy.^[173] Muslim thinkers, politicians and historians have drawn parallels between the crusades and modern political developments such as the mandates given for the governance of Syria, Lebanon, Palestine, and Israel by the United Nations.^[174] Right-wing circles in the Western world have drawn opposing parallels, considering Christianity to be under an Islamic religious and demographic threat that is analogous to the situation at the time of the crusades. Crusader symbols and anti-Islamic rhetoric are presented as an appropriate response, even if only for propaganda purposes. These symbols and rhetoric are used to provide a religious justification and inspiration for a struggle against a religious enemy.^[175] Some historians, such as Thomas F. Madden, argue that modern tensions are the result of a constructed view of the crusades created by colonial powers in the 19th century and transmitted into Arab nationalism. For him the crusades are a purely medieval phenomenon that can only be understood in the terms that the crusaders were engaged in acts of love and charity in a purely defensive war on behalf of their co-religionists.^[176]

Originally, medieval understanding of the crusades was narrowly focussed on a limited set of interrelated texts, most notably Gesta Francorum which possibly dates from as early as 1099. This created a papalist, northern French and Benedictine template for later works. These all demonstrated a degree of martial advocacy with both success and failure attributed to God's will.^[177] This clerical view was soon challenged by vernacular adventure stories based on the work of Albert of Aachen. The historian William of Tyre expanded on Albert's writing in his Historia. Completed by 1200 William's work describes the warrior state the Outremer had become through the tensions between the providential and secular.^[178] Largely, medieval crusade historiography remained more interested in presenting moralistic lessons than information, with the crusades as a moral exemplar and a cultural norm.^[179]

The attitudes to the crusades during the Reformation were shaped by the radical fragmentation of religious orthodoxy, the perceived threat of the Ottomans and the French Wars of Religion. Protestant martyrist John Foxe in his History of the Turks (1566) blamed the sins of Roman church for the failure of the crusades and condemned the use of crusades against those he considered had maintained the faith, such as the Albigensians and Waldensians. Lutheran scholar Matthew Dresser (1536–1607) extended this view. The crusaders were lauded for their faith but Urban II's motivation was seen as part of his conflict with German Emperor Henry IV. The crusade was flawed, the idea of restoring the physical Holy Places was “detestable superstition”.^[180] French Catholic lawyer Etienne Pasquier (1529–1615) is thought to be the first to number the crusades, he calculated there were six. His work reflected the damage that religious conflict had inflicted on France. It lists victims of papal aggression, sale of indulgences church abuses and corruption. The crusades had failed, damaged the church and led to conflict at home.^[181]

In The History of the Decline and Fall of the Roman Empire, 18th-century English historian Edward Gibbon wrote that the crusaders' efforts could have been more profitably directed towards improving their own countries.^[8] Jonathan Riley-Smith considers that much of the popular understanding of the crusades derives from the 19th-century novels of Walter Scott and the French histories by Joseph François Michaud. The crusades provided an enormous amount of source material, stories of heroism, and interest that underpinned growth in medieval literature, romance, and philosophy.^[92]

In modern historiography, the term "crusade" may differ in usage depending on the author.

Giles Constable describes four different perspectives among scholars:^[182]

The Muslim world exhibited little interest in European culture until the 16th century and in the crusades until the middle of the 19th century.

There was no history of the crusades translated into Arabic until 1865 and no published work by a Muslim until 1899.^[186] In the late 19th century, Arabic-speaking Syrian Christians began translating French histories into Arabic, leading to the replacement of the term "wars of the Ifranj" – Franks – with al-hurub al Salabiyya – wars of the Cross. Namık Kemal published the first modern Saladin biography in 1872. The Jerusalem visit in 1898 of Kaiser Wilhelm prompted further interest, with Sayyid Ali al-Hariri producing the first Arabic history of the crusades.^[173]