Crusading movement

The crusading movement began in 1095 with Pope Urban II's call for the First Crusade at the Council of Clermont, aiming to liberate eastern Christians and Jerusalem from Muslim rule. Associating warfare with the penitential practice of pilgrimage to the Holy Land, Urban granted spiritual benefits to participants. By then, church reforms had strengthened papal authority over Western Christendom, while conflicts with secular rulers fostered the concept of Christian holy wars, blending classical just war theories, biblical precedents, and Augustine's teaching on legitimate warfare. The idea of armed pilgrimage resonated with the Christocentrism and militant Catholicism of the age, prompting widespread enthusiasm. Economic expansion in Western Europe, the decline of traditional Mediterranean powers, and Muslim disunity facilitated western advance, allowing the crusaders to triumph and consolidate their conquests into four Crusader states. Their defence inspired further crusades, while the papacy extended the same spiritual benefits to campaigns against other opponents, including Muslims in Iberia, pagans in the Baltic, and rivals of papal authority across various regions.

The crusades gave rise to distinctive institutions and ideologies, leaving a profound mark on medieval societies across Europe and the Mediterranean. Although crusading appeals primarily targeted the warrior class by invoking chivalric ideals, the campaigns' success relied on the active involvement of other social groups, including clergy, burghers and commoners. Women, though discouraged from participating, were nonetheless involved—as crusaders, proxies for absent husbands, or victims. While many crusaders were drawn by the promise of crusade indulgence (the remission of sins), material incentives also played a role. Most crusades were launched via papal bulls, and participants signified their commitment by "taking the cross"—sewing a silk cross onto their robes. Those who failed to fulfill crusade vows faced excommunication. Periodic surges of popular enthusiasm sparked unsanctioned "popular crusades".

Initially funded through improvised means, crusades began, from the late 12th century onward, to rely increasingly on papal taxation of clerical income and the sale of indulgences. Their core forces consisted of heavily armed knights, supported by infantry and locally recruited troops, while naval power was largely supplied by Italian and Baltic city-states. To secure their conquests, the crusaders built formidable castles. The fusion of chivalric and monastic ideals gave rise to the military orders. Crusading campaigns extended Western Christendom's frontiers and established new polities in both the Mediterranean and northern Europe. While these outposts often endured into the early modern era, the Crusader states fell to the Mamluks of Egypt by 1291. In many regions, the crusades facilitated the blending of Western and local cultures and left a lasting legacy in European literature and art. Although core crusading institutions came under attack during the Reformation, anti-Ottoman "holy leagues" sustained the tradition into the early 18th century.

The crusades are commonly defined as religious wars waged by Western European warriors during the Middle Ages for the holy city of Jerusalem.^[1][2] However, their geographic scope, chronological boundaries, and underlying motives remain fluid in academic studies.^[3][4] The movement fostered distinct institutions and ideologies that shaped medieval society in Catholic Europe and neighbouring regions.^[5][6]

In classical antiquity, Greek philosophers and Roman jurists formulated just war theories that later shaped crusading theology. Aristotle stressed the need for a just end, asserting that "war must be for the sake of peace". Roman law required a casus belli—just cause—and held that only legitimate authorities could declare war, with defence, restitution, and punishment deemed acceptable grounds.^[7] Although the Bible—Christianity's core scripture—presents conflicting views on violence,^{[note 1][9]} the 4th-century Christianisation of the Roman Empire gave rise to Christian just war theory. Ambrose, a bishop and former imperial official, was the first to equate enemies of the state with those of the Church.^[10][11]

The empire was divided into two parts in 395.^[12] Fifteen years later, the sack of the city of Rome led Augustine—student of Bishop Ambrose—to write The City of God, a monumental historical study.^[13] He argued that the Bible's prohibition on killing did not apply to wars waged with divine approval.^[14] For Augustine, just war must be declared by legitimate authority, pursued for a just cause once peaceful means had failed, and conducted with restraint and good intent.^[10][15] His scattered reflections were nearly forgotten after the Western Empire's fall in 476.^[10][16]

From the ruins of the Western Roman Empire, new Christian kingdoms emerged, largely ruled by Germanic warlords. Among this aristocracy, martial prowess and comradeship were core values. Clergy often praised their violence in pursuit of patronage, though the Church still deemed killing sinful and required penance—typically fasting^[17]—for absolution.^[18]

Meanwhile, the Eastern Roman (Byzantine) Empire endured, though much of its territory, including Palestine, was conquered by the rapidly expanding Islamic Caliphate by the mid-7th century.^[19][20] Islam's holiest text, the Quran, contains verses on jihad—struggle to spread and defend the faith.^{[note 2][22][23]} In the early 8th century, Muslim forces entered Europe, conquering much of the Iberian Peninsula. Christians under Muslim rule were not forced to convert but had to pay a special tax, the jizya.^[24] As conquests stabilised, a threefold civilisational order emerged: a fragmented Western Europe, a weakened Byzantium, and an offensive Islamic world.

Christian resistance to Muslim expansion led to the creation of the small Kingdom of Asturias in north-western Iberia. Over time, this resistance evolved into an expansionist movement, regarded by locals as divinely sanctioned—a mission to reclaim lost Christian lands. In the 9th century, repeated invasions by non-Christian groups across Western Europe revived the notion of holy war:^[15] conflict authorised by spiritual leaders, pursued for religious aims and rewarded with salvation.^[25] Already in 846, Pope Leo IV promised salvation to those defending the papal territories.^[26][27]

As warfare became constant, a new military class of mounted warriors emerged. Known as milites in contemporary texts, they specialised in weapons like the heavy lance.^[28][29] To restrain their violence, church leaders launched the Peace of God movement.^[30][31] Ironically, efforts to curb bloodshed also militarised the Church, as bishops increasingly raised armies to enforce the Peace.^[32]

With weak central authority, regional strongmen seized control of parishes and abbeys, often appointing unfit clergy. Believers feared such irregularities invalidated sacraments,^[33][34] heightening anxiety over damnation.^[17][35] Sinners were expected to confess and perform penance to be reconciled with the Church. Since penance could be burdensome, priests began offering indulgences—commuting penance into acts like almsgiving or pilgrimage.^[36][37] Among these, penitential journeys to Palestine held special value, as it was the setting of Jesus's ministry^[38][39] and home to the Church of the Holy Sepulchre, believed to mark his crucifixion and resurrection.^[40][41]

Widespread fear of damnation spurred reform movements within the Church, often led by wealthy monasteries. In 910, Cluny Abbey's foundation charter set a precedent by granting monks the right to freely elect their abbot. The Cluniac Reform spread rapidly, backed by aristocrats who valued the monks' prayers for their souls.^[42][43] Cluniac houses answered solely to papal authority.^[44][45]

The popes, viewed as Peter the Apostle's successors, claimed supremacy over the Church, citing Jesus's praise for his apostle.^[46] In reality, Roman noble families controlled the papacy until Emperor Henry III entered Rome in 1053. He appointed reformist clerics who launched the Gregorian Reform for the "liberty of the church", which banned simony—the sale of church offices—and gave cardinals, senior clergy, sole right to elect the pope.^[47][48] Andrew Latham, a scholar of international relations, argues that the Gregorian Reform placed the Western Church in structural conflict with "a range of social forces within and beyond Christendom".^[49] By then, divisions in theology and liturgy between western and eastern mainstream Christianity had deepened,^{[note 3]} leading to mutual excommunications in 1054 and the eventual split between the western Roman Catholic and eastern Orthodox Churches, though communion was not entirely severed.^[50][51]

A spiritual revival took root as new monastic communities like the Carthusians and Cistercians emerged, and the Rule of Saint Augustine spread among secular clergy. Christocentrism—a renewed focus on Christ's life and sufferings—also shaped the period, inspiring itinerant preachers who often defied episcopal authority.^[52]

Four major powers dominated the Mediterranean c. 1000: the Umayyads in Al-Andalus (Muslim Spain), the Fatimids in Egypt, the Abbasids in the Middle East (at least nominally), and the Byzantine Empire. Within decades, all experienced serious crises, especially in the east, where climate anomalies triggered famine and instability.^[53][54] In contrast, climate change benefitted Western Europe, fuelling economic and population growth.^[55]

Weakened by internal conflict, Al-Andalus fractured into small Muslim states, vulnerable to Christian expansion—a process called the Reconquista.^[56] The historian Thomas Madden describes it as "the training ground" for the crusades, blending pilgrimage with anti-Muslim warfare.^{[note 4][57]} In Egypt and Palestine, repeated failure of the Nile's floods led to famine and growing interreligious tension. In 1009, the Fatimid caliph Al-Hakim ordered the destruction of the Holy Sepulchre,^{[note 5][59]} though it was later rebuilt with Byzantine support.^[60] Meanwhile, Turkoman migrations from Central Asia destabilised the Middle East. The Turkoman chief Tughril I, of the Seljuk clan, seized Baghdad in 1055;^[61][62] his successor, Alp Arslan, defeated the Byzantines at Manzikert in 1072, opening Anatolia to Turkoman settlement.^[63][64]

As traditional powers declined, Italian merchants gained control of Mediterranean trade.^{[note 6][65]} The Normans, rising from northern France, conquered southern Italy and Sicily by 1091.^[66][67] Their expansion threatened papal interests, prompting Pope Leo IX to launch a military campaign against them. Though his campaign failed, he had promised absolution to its participants^[68][69]—an early sign of the reform papacy's willingness to invoke spiritual incentives for warfare.^[70]

For Western warriors, warfare offered a path to land and power.^{[note 7][72]} These ambitions often aligned with reformist popes, who granted absolution to those fighting Muslim powers in Sicily and Iberia.^{[note 8][74][73]} As these territories were once Christian, papal attention soon turned to Palestine. Pope Gregory VII proposed a campaign to reclaim Jerusalem as early as 1074, though it never materialised.^[75] Two years later, disputes over clerical and royal authority ignited the Investiture Controversy, reviving interest in just war theory.^[76][77] Anselm of Lucca, a canon lawyer, compiled Augustine's writings to argue that war could, in some cases, be an act of love aimed at preventing sin. The theologian Bonizo of Sutri considered those who died in such wars martyrs.^[76][78] These ideas shaped the notion of penitential warfare: the belief that fighting for a just cause could serve as penance.^[79]

The fusion of classical just war theory, biblical views on warfare, and Augustine's teaching on legitimate violence provided the Western Church with an ideological framework for military engagement.^[74] By the late 11th century, Western Christendom had coalesced into a union of local churches under papal authority.^[80] Amid religious revival and heightened concern over sin, the papacy was well positioned to mobilise the warrior class's values, particularly loyalty.^[81]

Facing Turkoman incursions, the Byzantine emperor Alexios I Komnenos sought military aid from Pope Urban II. According to the historian Thomas Asbridge, Urban saw this as a chance to reassert papal authority. At the Council of Clermont in 1095, he called for a campaign against the Turkomans, offering spiritual rewards to participants.^[82][83] The historian Jonathan Riley-Smith views this as a "revolutionary appeal" that linked warfare to pilgrimage.^[79]

Urban's appeal sparked unexpected enthusiasm. In early 1096, 20,000–30,000 poorly organised crusaders set off in what became the People's Crusade—most perished or were massacred en route.^[84][85] A second wave followed between August and October, comprising at least 30,000 warriors and as many non-combatants, led by prominent aristocrats including Raymond of Saint-Gilles, Bohemond of Taranto, and Godfrey of Bouillon.^[86][87] They advanced through fragmented Muslim-held territories and captured the cities of Edessa, Antioch, and Jerusalem by July 1099.^[88][89]

The first Crusaders consolidated their conquests into four states: Edessa, Antioch, Jerusalem, and Tripoli. Their defence prompted new campaigns, the first as early as 1101. Several expeditions, especially those led by monarchs, became numbered.^[90][91] Edessa's fall in 1144 to the Turkoman leader Imad al-Din Zengi triggered the Second Crusade, led by Louis VII of France and Conrad III of Germany, which failed in 1148.^[92][93] Zengi's son, Nur al-Din, unified the Syrian Muslim states and dismantled the Fatimid Caliphate. These lands came under the control of Saladin, an ambitious Kurdish general. In 1187, he destroyed the Jerusalemite field army at Hattin and captured most Crusader territory, including the city of Jerusalem.^[94][95] The resulting crisis triggered the Third Crusade, led by Emperor Frederick I, Richard I of England and Philip II of France. Though Jerusalem remained under Muslim rule, the Crusader states endured, and the Kingdom of Cyprus was founded on former Byzantine territory.^[96][97]

Later crusades focused on recovering Jerusalem, but the Fourth was diverted by a Byzantine claimant, leading to the sack of Constantinople and the creation of a Latin Empire in the Byzantine Empire's ruins in 1204.^[98][99] The Fifth Crusade against Egypt failed in 1217–21. The Sixth regained Jerusalem in 1229 through negotiations by the excommunicated Emperor Frederick II, but the city was sacked in 1244 by Khwarazmian raiders.^[100] Its loss prompted Louis IX of France to launch a new crusade in 1248, which ended in defeat.^[101] Between 1250 and 1260, the Mamluks supplanted Saladin's family as the dominant Muslim power in the Middle East. They waged systematic campaigns against the Crusader states, massacring Christian populations. Louis IX mounted another crusade, but died in 1270. Civil war followed, and by 1291 the Mamluks had seized the last Crusader strongholds in the Holy Land.^[102] Despite continued proposals to reclaim Jerusalem,^{[note 9]} efforts were hampered by events such as the Hundred Years' War.^[104][105]

The historian Simon Lloyd notes that "crusading was never necessarily tied" to the Holy Land.^[106] As early as 1096, Pope Urban urged Catalan nobles to remain in Iberia, promising equal spiritual rewards.^[107] The First Lateran Council in 1123 officially equated campaigns against the Moors (Iberian Muslims) with crusades.^[108][109] The Iberian crusades drove Christian expansion, reducing Al-Andalus to the Emirate of Granada by 1248.^{[note 10][110]}

Some crusades emerged from conflict with pagan groups.^[112] In 1107–08, Saxon leaders referred to the pagan Slavic Wends' territory as "Our Jerusalem", though anti-Wendish war was only recognised as a crusade in 1147. From then, northern German, Danish, Swedish, and Polish rulers launched papally sanctioned campaigns against Slavic, Baltic and Finnic tribes—collectively termed as the Northern Crusades. By the 1260s, leadership had passed to the Teutonic Order's warrior monks.^[113][114]

Crusading zeal also turned against Christian foes of the papacy. So-called "political crusades" were launched against Emperor Frederick II, his heirs, and rebellious papal vassals.^{[note 11][116]} From 1209, Pope Innocent III targeted heretics—Christians who rejected Church doctrine—^[117]and crusades were proclaimed after 1261 against the restored Byzantine Empire.^[118]

Despite internal divisions, the Reconquista continued, ending with the conquest of Granada by Castile and Aragon in 1492.^[119][120] In the early 14th century, Preussenreise—seasonal anti-pagan expeditions by Catholic nobles in the Baltic—became a hallmark of chivalric culture.^[121] The historian Eric Christiansen called these "an interminable crusade".^[122][123] In the western Mediterranean, popes also proclaimed crusades against Christian enemies, including Aragon, Sicily, and rogue mercenaries. During the Western Schism (1378–1417), rival popes called crusades against each other's supporters.^{[note 12][125][126]}

Extensive piracy in the Mediterranean revived anti-Muslim crusading in the mid-14th century.^{[note 13][128]} International campaigns targeted the rising Ottoman Empire but failed to stop the fall of Constantinople in 1453.^[129] The Hussite Wars reignited anti-heretical crusades in 1420,^[130][131] while the Reformation saw indulgences granted to Catholics fighting Protestants, including Irish forces opposing Queen Elizabeth I.^[132] Although the Reformation weakened papal authority, the papacy continued to promote anti-Ottoman crusades, helping form coalitions like the Holy League well into the late 17th century.^[133][134]

Pope Urban II's call at Clermont introduced a remarkably novel concept for most listeners.^[135] Though Western Christians had accepted divinely sanctioned warfare, its full theological and legal justification was still evolving.^[136] Urban emphasised the expedition’s military character, but his envoys presented it largely as a pilgrimage.^[137]

Initially seen as a unique event attributed to divine intervention, the expanding movement soon demanded a stronger legal basis. Canon lawyers developed frameworks to support papal authority.^[138] The Decretum Gratiani, an influential collection of church law, permitted warfare c. 1140—but only against heretics.^[139][140] Within decades, jurists like Huguccio extended this to Muslims, citing just intent, recovery of Christian lands, and retaliation for violence.^[140] Initially framed as defensive, the Northern Crusades soon focused on conversion, especially during the early 13th century.^[141] Crusades against Christian opponents of the papacy were justified as necessary to remove obstacles to the defence of the Holy Land.^[142]

Soon after Clermont, the chronicler Guibert of Nogent wrote that "God has instituted in our times holy wars" so both knights and commoners might gain salvation.^[79] Yet the nature of the spiritual rewards granted to the First Crusaders remains unclear. Some sources mention cancellation of temporal penance, others full remission of sins.^{[note 14][144][83]} Pope Urban referred to remissio peccatorum ('remission of sins') in one letter, and in another promised absolution of all penance to those travelling to the Holy Land "only for the salvation of their souls", provided they confessed.^[145] His successors used identical or similar phases, such as peccatorum absolutionem ('absolution of sins') and venia peccatorum ('forgiveness of sins').^[146]

Theological debate on indulgences began c. 1130. Peter Abelard sharply criticised the practice, though most later theologians accepted it.^[147] The Fourth Lateran Council standardised crusade indulgences in 1215, declaring that "sins repented by heart and confessed with mouth" would be remitted. The theological basis remained unsettled until c. 1230, when the "Treasury of Merit" doctrine emerged. It held that the Church could grant indulgences from merit earned through Christ and the martyrs.^[148][149] Debate over the indulgences' scope continued. Bonaventure argued indulgences did not apply to those dying before fulfilling their vow, while Thomas Aquinas maintained that penitent crusaders who confessed their sins would attain salvation even if they died before departing.^[150]

A crusader's motives are inherently difficult to determine. While contemporary sources emphasise religious fervour, secular ambitions also played a role, since holding conquests required sustained Western presence.^{[note 15]} Many participants, including non-combatants, enlisted for pay.^[152] Most crusaders saw no contradiction between religious devotion and material gain, such as booty.^[153][154] Some sought fame, while the historian Jonathan Phillips highlights the appeal of long-distance travel.^[155] The medievalist Andrew Jotischky suggests that some, including the robber baron Thomas of Marle, viewed the crusades as an opportunity for unpunished violence.^[156]

Born into the French nobility, Pope Urban directed his appeal at Clermont to the country's military elite.^[157] By then, the milites—once a broad category—had become a distinct warrior caste, though knighthood would not be fully equated with nobility until the late 12th century.^[158] Aristocrats valued visible acts of piety, and crusading offered a new outlet for what Madden calls their "simple and sincere love of God".^[159] The warrior lifestyle entailed habitual sin, yet offered few chances for penance. Barefoot pilgrimages stripped knights of their symbols—arms and warhorses. Urban's message provided a way to maintain their identity without endangering salvation.^{[note 16][161][160]} Crusade rhetoric reflected their values, invoking vassalage and honour.^[162] Preachers cast Christ as a feudal lord, summoning knights to defend his stolen patrimony as milites Christi ('Christ's warriors').^{[note 17][164][151]}

Crusading decisions were often collective, made within noble households led by influential lords. Success brought prestige,^{[note 18]} and the example of crusading relatives could turn participation into a family tradition.^{[note 19][167]} Yet failed expeditions risked disgrace and financial ruin.^[165][168] As late as the Late Middle Ages, chivalric ideals fuelled two expeditions: the 1390 Barbary Crusade and the 1396 Crusade of Nicopolis.^[169]

Although violence conflicted with their vocation, clergy often joined crusades.^[170] At Clermont, Bishop Adhemar of Le Puy was first to vow the journey to Jerusalem.^[171] The Fourth Lateran Council explicitly permitted clerics to join crusades for up to three years without forfeiting their benefices.^[172] Secular clergy typically served as chaplains or administrators,^[173][174] while senior churchmen sometimes led troops.^{[note 20][174]} Influential prelates also helped initiate the Northern Crusades.^{[note 21][179]} Despite vows like stabilitas voci ('stability of place'), monks joined as well.^[170][173] Cistercian and Premonstratensian occasionally took up arms, especially in the Baltic.^{[note 22][181]}

Urban elites played a vital role in several crusades.^[182] Fleets from Genoa, Pisa, and Venice helped establish and secure the Crusader states.^{[note 23]} In return, they gained commercial privileges, city quarters, and sometimes rural estates.^[184] Lübeck supported the conquest of Prussia,^[185] while Iberian towns owed military service under royal charters—often replaced by a special tax called fonsadera.^[186]

During the Fourth Crusade, Doge Enrico Dandolo convinced fellow leaders to seize Zadar, a Catholic city on the Dalmatian coast, and later advocated the assault on Constantinople. After its sack, Venice gained control of several Aegean islands, establishing patrician-led lordships.^{[note 24][189][190]} Marino Sanudo Torsello, a Venetian writer, emerged as a key theorist of crusading.^[191] He first proposed a naval alliance against Aegean pirates, uniting Catholic powers with Genoese and Venetian island lords.^[191] Pope John XXII endorsed the plan in 1334.^[192]

The historian Christopher Tyerman observes that crusading was "as much as a phenomenon of artisans as of knights, of carpentry as much as of castle". Commoners filled essential roles in crusader armies as foot soldiers, sailors, archers, engineers, and squires. They were typically young men of modest means who joined for pay. Thus, Tyerman notes, "the image of crowds spontaneously leaving fields or workshops to follow the cross is largely mythical".^[193]

Following Clermont, Pope Urban barred clergy from accepting vows from those unable to fight and annulled existing ones.^[194] Nonetheless, the People's Crusade consisted almost entirely of unarmed commoners,^[195] inspired by unauthorised preachers like Peter the Hermit, whom many viewed as a living saint.^[196] In the First Crusade's noble-led armies, non-combatants nearly matched the number of fighters. The historian Conor Kostick describes them "a slice of European society on the march".^[197] Chroniclers like Raymond of Aguilers called common crusaders as pauperes ('the poor or defenceless') and deemed their presence vital for divine favour. Another label, rustici, reflected their rural origin.^[198] Unlike nobles, captured commoners were often tormented or killed rather than ransomed.^[199]

Grassroots crusading zeal inspired later mass movements known as popular crusades.^[200][201] These included the 1212 Children's Crusade, led by two charismatic boys;^{[note 25]} the 1251 and 1320 Shepherds' Crusades, the former sparked by a letter allegedly from the Virgin Mary; and the 1309 Crusade of the Poor. None reached the Holy Land, and both Shepherds' Crusades were forcibly disbanded.^[203][204] In 1456, a peasant crusader army helped repel the Ottomans at the Siege of Belgrade. This success encouraged future efforts to mobilise peasants in anti-Ottoman crusades, but in 1514 a crusading peasant army in Hungary turned on their lords.^[205]

Muslim legal experts divided the world into two spheres: Dar al-Islam (the Muslim world) and Dar al-harb (the non-Muslim realms). Border regions like Syria and Iberia became jihad battlegrounds, attracting volunteers—mujahideen and ghazis—from the Muslim world.^[206][207] Accounts on Christians' experiences in the Holy Land on the eve of the First Crusade vary.^{[note 26][208]} While attacks on pilgrims likely contributed to the perception that Christians were endangered,^[209] Asbridge stresses that interfaith violence reflected the era's broader political and social unrest.^[210]

Western Christians often mislabelled Muslims as idol-worshippers or heretics.^{[note 27][212][213]} Until c. 1110, mass killings of Muslims in conquered towns were not unusual.^{[note 28][215][216]} Later, Crusaders rarely attempted conversion, instead levying a poll tax akin to the jizya.^[217] Though church law imposed various restrictions upon Muslims, their enforcement is poorly documented.^{[note 29][218]} In the Crusader states, most Muslims were Arabic-speaking farmers who lived in communities under their own leaders, governed by Islamic law.^[219] In Iberia, the mudejares—Muslims under Christian rule—also faced second-class status.^{[220][221][222]}

Initially, few Muslims grasped the religious nature of the crusades. The Damascene scholar Ali ibn Tahir al-Sulami was the first to frame the crusades within the wider expansion of the "Franks", or westerners, across the Mediterranean.^[23][223] He interpreted their success as divine punishment for neglecting jihad.^[224] Zengi was among the era's first Muslim leaders to be honoured with jihadist titles; over time, other rulers also emphasised religious motives in campaigns against the Franks.^[225] In Iberia, the Almoravids and the Almohads were ardent champions of jihad.^[226] Nonetheless, pragmatic Christian–Muslim alliances were frequent over the crusading period.^{[note 30][230][231]}

The liberaton of eastern Christians was declared a central aim of the First Crusade, yet initial encounters proved disappointing.^[233] The arrival of Crusaders unsettled Emperor Alexios, who had anticipated disciplined mercenaries or manageable allies. Concerned by the crusade leaders' territorial ambitions, he secured oaths guaranteeing the return of reconquered Byzantine lands.^[234] Nonetheless, Bohemond retained Antioch—a former Byzantine provincial capital—for himself.^[235] Soon after its capture, Crusader leaders described local Christians as "heretics" in a letter to Pope Urban.^[236] In 1099, Catholic clergy temporalily excluded native clerics from officiating at the Holy Sepulchre.^{[note 31][238]} In the Crusader states, Eastern Christians paid a poll tax, signalling their subordinate status, although self-governance was maintained^[239] and some retained considerable landholdings.^[240]

Orthodox Christians—known as Melkites—formed the majority of the native Christian population in Palestine and were also prominent in northern Syria.^[241] Regarded as schismatics rather than heretics, they received limited recognition. John the Oxite, the Orthodox patriarch of Antioch, was reinstated before being exiled in 1100. While most Orthodox bishops had fled Palestine before 1099, scattered references suggest the presence of an Orthodox hierarchy under Frankish rule.^{[note 32][243]} Monasticism experience a revival under Byzantine patronage.^[244]

Unlike the Catholics and Orthodox, certain eastern Christian communities rejected the Christological rulings of the Council of Chalcedon. Among these, the Armenians—predominantly in northern Syria and Cilicia^[245]—were the most respected by the Franks, largely due to their autonomous lordships.^[246] Many Armenians welcomed the Crusaders, and some formed marriage alliances with them. This collaboration led to a tenuous church union with Rome (1198),^[247] and ultimately the Frankish Lusignans' rule over Cilician Armenia.^[248] Syriac (or Jacobite) Christians, mainly rural and Arabic-speaking, were viewed with suspicion and condescension.^[246] Another distinct group, the Maronites of Mount Lebanon entered into communion with Rome, forming the first Eastern Rite Catholic Church in 1181.^[249]

Relations between Byzantines and the Crusader states fluctuated.^[250] Following the Fourth Crusade, successor states such as Epiros and Nicaea spearheaded Greek resistance, though temporary Greek–Frankish alliances were not uncommon.^{[note 33][252]} In Frankish Greece, many Greek árchontes (aristocrats) retained their estates and fought alongside Franks, while peasants faced harsher conditions than under Byzantine rule.^[253] Orthodox bishops who rejected papal supremacy were replaced by Catholic apointees, but the papacy protected Greek monasteries.^[254] The Frankish conquest reinforced Orthodox identity, and persistent local resistance ultimately thwarted attempts to church reunification.^{[note 34][256]}

In northeastern Europe, Catholic and Orthodox churches coexisted in major trading centers, and the schism did not impede dynastic intermarriage. Catholic missionary activity only intensified after the Fourth Crusade. Despite occasional alliances between Crusaders and Rus' leaders, no lasting control of Rus' territory was achieved.^[257]

Trade in raw materials and slaves had established lasting contact between Christian and pagan communities in the Baltic region well before the crusades, though rivalries over trade routes often escalated into open conflict.^[258] Intensified German colonisation and the unequal access to natural resources led to more frequent clashes between the Wends and their Christian neighbours from c. 1100.^[259][260] When promoting the Second Crusade in 1146, the Cistercian Bernard of Clairvaux found the Saxon lords unwilling to abandon their campaigns against the Wends for a journey to the Holy Land. Viewing pagan conversion as essential for the Devil's ultimate defeat, he adopted their perspective, and convinced Pope Eugenius III to authorise an anti-Wendish crusade.^[261][262] The Wends' structured society, with principalities, towns, and priestly hierarchy, eased their integration into the Christian world.^{[note 35][265]}

To the east, Baltic peoples had resisted Christian proselytism for centuries. Most—such as the Old Prussians, Latvians, Curonians—lived in rural communities led by local strongmen who amassed wealth through trade and raiding.^[266] Crusaders used coercion and bribery, and promises of protection from mutual enemies to secure conversions.^[267] Though papal legates made repeated efforts to shield converted Balts from exploitation, they achieved little success.^{[note 36][268]}

The Lithuanians, the fourth major Baltic group, were mostly peasants owing taxes and services to native lords. Surrounded by external threat, Lithuania unified under Grand Prince Mindaugas in the 13th century. He was baptised and received a royal crown from Pope Innocent IV in 1253, but his successors reverted to paganism and extended control over Orthodox Rus' principalities like Polotsk and Kyiv.^[270] In 1386, Grand Prince Jogaila married Queen Jadwiga of Poland and became King Władysław II. The resulting mass conversion of Lithuanians to Catholicism undermined the Teutonic Knights' justification for continued anti-Lithuanian crusades. In 1410, Polish and Lithuanian forces decisively broke the Knights' power at Tannenberg. The Preussenreise lost popularity, and the last non-German crusaders entered the Baltic in 1413.^[271][272]

In the easternmost Baltic, Finnic peoples lived in small rural communities. Alongside agriculture and slave-raiding, they hunted for valuable furs.^[273] Legend holds that the Swedish king Eric IX launched the first crusade into Finland in the late 1150s, but the earliest confirmed crusade was proclaimed by Pope Gregory IX in 1237.^[274][275] Danish crusaders conquered Estonia in 1219, though by mid-century, German knights and burghers had come to dominate the region's political life.^[276]

The Gregorian Reform failed to satisfy those seeking a purer, simpler form of Christianity. The Waldensians, the first significant dissident group, praised poverty and preached in the vernacular.^[277] Increasing trade facilitated the westward spread of dualist ideologies, which distinguished between a pure, incorruptible God and an evil creator of the material world, rejecting the mainstream Christian doctrine of the Incarnation. In Western Europe, these groups became known as Cathars or Albigensians.^[278]

Catholic churchmen viewed heresy as a fundamental threat to Christianity and believers' salvation.^[110] As early as 1179, the Third Lateran Council endorsed the use of force against heretics and promised indulgences to those who fought them.^[279] However, Cathars were well integrated into Occitan society in southern France, and local elites were often unwilling to act against heretical family and friends.^[280]

In 1207, Pope Innocent III urged Raymond VI, Count of Toulouse, to eradicate heresy from his territories. Raymond's reluctance or inability to respond led the papal legate Peter of Castelnau to excommunicate him. The legate was soon murdered, prompting Innocent to declare a crusade.^[281][282] Crusaders, mostly from northern France, invaded Occitania, committing brutal acts against both Cathars and Catholics.^{[note 37][284]} While the campaigns deepened French control over the region, it failed to eliminate heresy. That goal was eventually achieved by mendicant friars and inquisitors with support from secular authorities.^[285]

In northern Germany, a crusade targeted peasants accused of heresy and witchcraft for refusing to pay the tithe (church tax).^[286] Hungarian rulers, aiming to expand into Bosnia, launched two failed crusades against the region, allegedly home to a Cathar antipope.^[287] In contrast, the Apostolici, a radical dissident group in northern Italy, were decisively eradicated by Crusaders.^[288]

Western Europeans first became aware of the Mongol conquests during the Fifth Crusade.^[289] The Mongol Empire had emerged in 1206 when the talented military commander Temüjin was proclaimed supreme ruler as Genghis Khan.^[290] Some Mongol tribes followed the Eastern Syrian (or Nestorian) Church.^[291] Although Nestorians had separated from mainstream Christianity in 431,^[292] fragmented reports about Mongol advance revived legends of a powerful eastern Christian ruler, Prester John, a potential ally against Islam.^[293]

The Mongols, however, were convinced they were divinely destined to conquer the world.^[294] Their devastating invasion of eastern and central Europe in 1239–40 deeply shocked Western Christendom. Pope Gregory IX called for a crusade, but the Mongols withdrew only because of the death of Genghis's successor, Ögedei Khan in late 1241.^[295][296] In 1258, Mongol forces captured Baghdad and destroyed the Abbasid Caliphate. Seeking protection, the Cilician Armenian king Hethum I and his son-in-law, Bohemond VI of Antioch submitted to Hulegu, the Mongol il khan (ruler of the Middle East). Mongol expansion in the region was brought to halt when the Mamluks defeated Hulegu's forces at Ain Jalut in 1260.^{[note 38][298]}

Roman legislation under the first Christian emperor Constantine the Great and Augustine's theological works laid the foundation of the Western Christians' general attitude to Judaism. Constantine recognised Judaism as a legal denomination but restricted the Jews' rights; Augustine admitted that the Jews were protected by God, but also stated that God had punished them with their dispersion for having failed to recognise Jesus as the godly appointed Messiah.^[299] The Jews' expansion in Western Europe began in parallel with the economic boom that preceded the crusades.^[300] Coming from the developed Islamic economies, Jewish merchants applied advanced commercial know-how. As they could ignore the anti-usury decrees of canon law, they quickly took control of moneylending, which reinforced antisemitism.^[301]

The local rulers mainly appreciated the Jews' economic role and offered them protection, but this protection was fragile in a hostile environment. As early as 1010, distorted news of the destruction of the Holy Sepulchre triggered antisemitic attacks in the towns of Limoges, Rouen and Mainz.^[300] The western Jewish communities first faced coordinated pogroms in the Rhineland at the beginning of the First Crusade. The crusaders reportedly wanted to take vengeance on the Jews for Christ's crucifixion, but their desire to seize Jewish property is well-documented.^[302][303] In the east, the Jews of Jerusalem were slaughtered by the first crusaders.^[304] The Jewry of other towns (such as Tyre and Ascalon) survived, and Jewish pilgrimage to the Holy Land intensified from the 12th century, leading to the settlement of hundreds of western Jews in Palestine.^[305]

Preaching for crusades led to antisemitic attacks throughout the 12th century. In 1146, the renegade monk Radulph stirred up pogroms in Rhineland, but Bernard of Clairvaux ordered his imprisonment. In 1189 and 1190, the mob attacked Jews in English towns.^[306][307] Antisemitism escalated to a new level with the spread of unfounded gossip about the ritual murder of Christian children by Jews from c. 1150.^[307]

Women were closely associated with the movement from its beginning.^[308] Although popes discouraged female participation, female servants always accompanied crusading armies.^[309] Among them, washerwomen received special papal authorisation early on.^[310] While women needed the permisson of a father or husband to join a crusade, from 1209 men could decide without their wives' consent. High-ranking women occasionally led troops or conducted key diplomatic negotiations.^{[note 39][312]} In the Baltic, female settlers actively participated in the defence of towns and villages.^[313] Sex workers also followed the armies though they were frequently expelled as part of purification efforts.^[309]

Gender-based bias is well documented among both crusaders and their opponents.^[314] Christian chroniclers primarily highlighted women's supportive roles—delivering water or stone missiles—but rarely mentioned female fighters.^[315] By contrast, Muslim and Byzantine writers often described armed female crusaders, framing them as symbols of barbarism.^[316] Muslim sources also condemned the relative freedom women in Frankish societies, viewing it as a gateway to debauchery.^[317] Crusaders were expected to abstain from sex, often leading to women, including wives, being banished before major battles.^[318] Women left behind by crusading husbands or fathers were vulnerable to exploitation by kinsmen and neighbours.^{[note 40]} Some Crusaders made formal arrangements with kin or religious institutions to protect their wives and daughters; others entrusted their wives or mothers with managing their estates.^{[note 41][321]}

Raids by both Christian and Muslim forces often targeted women, and after battles or sieges, victors frequently captured enemy women (and children).^[322] The First Crusade was an exemption: the crusaders often massacred entire populations of captured towns.^[323] In the Baltic, the Livonian Rhymed Chronicle praised the slaughter of pagan women and children as divinely-approved.^[324] Captured women were frequently raped.^[325][326] Noblewomen were held for ransom, though their value was usually lower than that of male counterparts. Those not ransomed were enslaved or married off.^[327]

Because of the high mortality of male warriors, women often inherited fiefs in the Crusader states, though they were expected to marry.^[328] Women could also inherit thrones: between 1186 and 1228, four queens ruled Jerusalem.^{[note 42][331]} In Frankish Greece, the wives of Achaean barons captured in the Battle of Pelagonia formed the "Parliament of Dames" in 1261 to negotiate peace terms with the Byzantine Empire on their husband's behalf.^[332]

Tyerman notes that the "crusade paraded across society in recruitment, funding and social rituals of support". The movement was accompanied by various elements such as public processions, priestly blessings, acts of charity, and objects of visual art.^[333] Since the movement’s first century coincided with the so-called "Twelfth-Century Renaissance", a period marked by the rise of vernacular literature, it also inspired literary works.^[334]

Most crusades were proclaimed by the pope, as only the Holy See could grant crusade indulgences. Calls for crusades typically appeared in papal bulls, outlining the causes, urging participation, and detailing the spiritual and secular benefits offered to participants.^{[note 43][336][337]} Crusade encyclicals were recited in all Catholic churches from the time of Pope Alexander III.^[338] Pope Gregory IX authorised the Dominicans to preach Baltic crusades without further approval,^[339] a privilege later extended to the Franciscans and the Teutonic priests.^[340]

Crusades were promoted by clerics. Prelates holding legatine powers typically addressed aristocratic audiences during significant secular or church assemblies. Preaching in towns and villages was initially disorganised. Pope Innocent III set up special committees to cooperate local propaganda campaigns, but later popes preferred less formal methods. From the early 13th century, mendicant friars, trained for missionary tasks, took charge of local crusade preaching. By the end of the century, priests commonly utilised handbooks written by prominent crusade propagandist, like the Dominican friar Humbert of Romans.^[341] These sermons opened with a brief tale or moral anecdote introducing the call for the crusade.^[342]

Individuals who choose to join a crusade made a public and solemn vow. Either at the same event or during a separate ceremony, a cloth or silk cross was sewn onto their mantle or robe. While red was the customary colour, other shades were occasionally used. By "taking the cross", crusaders demonstrated their commitment to follow Christ's call: "If any man will come after me, let him deny himself and take up his cross and follow me".^[343][344] The symbol aligned with the 11th-century imitatio Christi ('imitation of Christ') movement, promoting an active apostolic life.^[52] Some crusaders also received traditional pilgrim emblems—a pouch and staff.^[345]

Crusaders were required to wear the cross until their return, and those who removed it prematurely faced church censure for breaking their vow.^{[note 44][347]} Suspension, commutation, or cancellation of the vow was permitted only in exceptional cases, including physical or mental weakness, or poverty.^[348] Wearing the cross became the crusaders' defining emblem, and by the late 12th century, they were commonly known in Latin as crucesignati ('signed with the cross').^[349]

The secular privileges offered to the first crusaders are poorly documented. According to a collection of canon law, crusaders and their goods were "under the Truce of God"; likewise, Guibert of Nogent notes that Pope Urban extended papal protection to the crusaders, their family, and property. Years later, his successor Pope Paschal II instructed French prelates to ensure returning crusaders recovered their property as Urban had "ordained in a synodal declaration".^[350] In 1107, the canonist Ivo of Chartres still referred to this legal protection as "new".^{[note 45][352]} The First Lateran Council later codified these privileges, placing the crusaders' "houses and households" and property under ecclesiastical protection, and ordering the excommunication of anyone seizing them. This penalty was latae sententiae, or automatic, requiring no formal trial.^[353] Pope Eugenius III banned legal proceedings against crusaders and exempted them of paying interest on debts.^[354][355] However, papal protection was not always effective: Richard I of England was imprisoned in Austria on his return from his crusade.^[356]

Crusades, underlines the historian Simon Lloyd, were "crippingly expensive", even though the precise costs of individual campaigns are rarely documented.^{[note 46][357]} Scholars estimate that an ordinary knight spent more than four years' income to participate.^[358] To finance their expeditions, wealthy crusaders often sold commodities—typically timber—or granted privileges to towns or rural communities for a lump sum.^{[note 47]} While the outright sale of inherited estates was less frequent, mortgaging family lands or transferring them in vifgage—allowing creditors to be repaid from the property's income—was common. Crusaders also relied on gifts or loans from relatives, lords, or friends.^{[note 48][361]} In Iberia, regular tribute extracted from Muslim rulers enabled the Christian kings to reward their vassals with stipends.^[362]

From the mid-12th century, taxation became a key founding source. A special tax for the Holy Land's defence was introduced in France and England in 1166. In 1188, the "Saladin tithe"—a ten percent levy on income and property—was imposed in both kingdoms to fund the Third Crusade, though tax compliance, especially in France, was inconsistent.^[363] The first papal order to tax church revenues for crusading came in 1199 under Pope Innocent III. In 1274, Pope Gregory X detailed procedures for assessing and collecting this tax, though clergy often tried to avoid payment.^[364][365] From 1199, donations were collected via chests placed in churches.^[366] In 1213, Pope Innocent III introduced a novel fundraising mechanism, authorising everybody—except monks—to take a crusade vow, but also permitting them to redeem it through a cash payment.^[367][368] Purchasing indulgences remained the most common form of crusading into the early modern period, despite their high cost.^{[note 49]} As printing technology spread from the mid-15th-century, indulgence sheets were mass-produced with blanks for beneficiaries' names.^[369]

Command during most crusades was divided and uncertain, and desertion from the armies was not uncommon.^[370] Yet crusader morale was often boosted by visions, processions, and relics.^{[note 50][371][372]} Raids and battles were central to warfare in both Western Europe and the Middle East, but for most crusaders, besieging fortified urban centres—a standard feature of Levantine warfare—was unfamiliar. Raids primarily aimed at booty, destruction, or preparing major invasions.^[373] Crusaders generally avoided pitched battles, as defeat could result in devastating losses of troops and territory.^{[note 51][374]} Siege warfare relied heavily on stone-throwing engines, siege towers and battering rams. Muslim defenders often employed Greek fire, but crusaders learnt to counter it using hides soaked in vinegar.^[377] From the late 13th century, most plans for the recovery of the Holy Land distinguished two types of campaigns: a preliminary passagium particulare for establishing a bridgehead for the large-scale passagium generale.^[103]

Knights, the core of crusader armies, were heavily armoured horsemen.^[378] The historian John France describes them as the "masters of close-quarter warfare". In the east, they primarily faced mounted archers and relied on infantry support, particularly bowmen and spearmen.^[379] The Franks also hired native light cavalrymen, or Turcopoles, to harass and capture enemy troops.^[380] In the north, Teutonic Knights employed converted Prussians to raid pagan settlements.^[381] Almogavars—Spanish raiders—mainly used daggers, short lances and darts.^[186]

Naval force for Levantine crusades were chiefly suplied by Italian city-states and the Byzantines. Egypt maintained the only Muslim fleet in the eastern Mediterranean, but its small ships rarely threatened Western naval dominance. After Emperor Frederick I's failed overland crusade, all subsequent Levantine campaigns were transported by sea.^[382] In the north, large Scandinavian and German merchant vessels, capable of carrying 500 people, easily overcame the Baltic peoples' raiding-crafts and long-ships.^[383]

Across all territories conquered by the crusaders, castles were constructed to function as both military bases and administrative centres. These fortifications often blended Western European engineering with local building traditions. In the Levant, Norman-style fortified towers were initially built, but the Franks soon adopted the local castra layout of walled courtyards. This evolved into concentric castles with dual defensive systems, capable of withstanding sieges for months.^{[note 52][385][386]} Built on rocky hilltops, and heavily fortified with towers and a keep, spur castles represent "the most spectacular examples of Frankish military architecture", according to Phillips.^{[note 53][387]} In Iberia, over 2,000 castles were built on frontier promontories, enabling their garrisons to monitor enemy movement.^[388] The Teutonic Knights first raised blockhouses to defend their Baltic territories, but by c. 1250 began consructing stone towers. In the 14th century, stone was largely replaced by cheaper, more readily available brick.^[389]

Tyerman argues that the military orders "provided crusading's most original contribution to the institutions of medieval Christendom". These religious orders followed monastic rules but were dedicated to fighting for fellow Christians.^[390][391] The first military order was initiated by the French knight Hugues de Payens and his companions who decided to protect pilgrims in the Holy Land. In 1119, they took the three monastic vows of chastity, poverty and obedience, forming a confraternity. Official recognition came in 1120, and they became known as the Knights Templar after King Baldwin II of Jerusalem granted them chambers in the former Al-Aqsa Mosque, associated with the Temple of Solomon.^[392][393]

The concept of warrior-monks was revolutionary yet aligned with contempory chivalric and ecclesiastical ideals.^[394] By c. 1130, Bernard of Clairvaux praised the Templars as a "new knighthood".^[395] The Templars inspired other groups, primarily in borderlands of Latin Christianity.^[396] In the Holy Land, the militarisation of nursing confraternities led to the formation of military orders—the Knights Hospitaller, the Teutonic Knights, the Knights of Saint Thomas, and the Lazarists.^[397][396] In Iberia, royal support helped to establsh the Orders of Calatrava, Santiago, Alcántara and Aviz. In the Baltic, the Sword Brothers and Order of Dobrzyń, founded by local bishops, merged into the Teutonic Order by 1230.^[398][399] The papacy endorsed the Iberian and Baltic crusades by granting crusade indulgences to participants in campaigns lanched by the Orders of Alcántara (1238), Calatrava (1240), or the Teutonic Knights (1245).^[400][339]

Military orders were organised by function: the knight-brothers and servientes were armed monks; priest-brothers handled spiritual care; nobles could temporarily join for spiritual rewards; and others supported the order financially.^[401] The Templars and Hospitallers became the most powerful, owning estates across Latin Christendom and evolving into autonomous international organisation led by elected grand masters.^[402][403] Their convent networks facilitated the transfer of goods and cash, with the Templars becaming mayor players in money markets.^[404] Time to time, clerics and scholars criticised the military orders for greed, pride, and adopting non-Christian customs.^[405]

With the fall of the Crusader states, many military orders lost their justification for existence, intensifying criticism against them. The Templars faced particularly harsh scrutiny, as fighting Muslims was their sole purpose.^[406] In 1307, all Templars were arrested in France on charges of apostasy, idolatry and sodomy by order of King Philip IV. Despite no physical evidence supporting the accusations, the Order was dissolved without a hearing at the Council of Vienne in 1312.^[407] The Hospitallers survived, assuming responsibility for protecting shipping in the Mediterranean. Despite secularisation during the Reformation, the Teutonic Knights endured in Germany under Habsburg leadership. Iberian military orders gradually lost their religious character, as they affiliated with the Spanish and Portuguese Crowns, receiving papal dispensations from monastic obligations.^[408]

The four Crusader states secured Catholic control of the Holy Land, sustained by military and financial support from Catholic Europe. Edessa, the earliest and most vulnerable, fell after a misguided alliance with Zengi's Muslim rivals, the Artuqids.^[409] Internal factionalism weakened Jerusalem, leaving it unable to resist Saladin's 1187 invasion, though the Third Crusade restored Frankish control along the coast.^[410][411] In the north, Antioch and Tripoli formed a personal union following the War of the Antiochene Succession.^[412] After Frederick II's crusade, absent kings left Jerusalem governed by regents, sometimes chosen by their opponents.^[413] By the Mamluk advance, the Crusader states had splintered into warring autonomous communities led by Frankish lords, urban communes, Italian merchants, and military orders.^[414]

Just a day's sail from Syria, Cyprus became a key supply base for Levantine crusades and a refuge for mainland exiles.^[415] From 1269, its kings also claimed Jerusalem, though the Sicilian Angevins contested this from 1277.^[416] After the Black Death struck the island in 1347–48, shifting trade routes weakened its main port, Famagusta. Peter I of Cyprus launched a crusade against Alexandria, Famagusta's Egyptian rival, threatening Genoese trade. In response, the Genoese sacked Famagusta and imposed tribute on Cyprus. Later, the island became a corsair haven, prompting the Mamluk invasion in 1426. After the Lusignan line ended in 1474, the Venetians assumed control, but lost the island to the Ottomans in 1570-71.^[417]

Months before Constantinople's sack, the leaders of the Fourth Crusade agreed to partition the Byzantine Empire: an elected emperor would receive a quarter of the territory, the rest going to other Frankish leaders and Venice.^[418][419] Frankish Greece proved more stable than the Crusader states and attracted more Western settlers.^[419] Rising demand for goods such as wheat, olive oil and silk enriched the Frankish lords of the Peloponnese, turning the court of the Villehardouin princes of Achaea into a center of chivalric life.^[420][421] Achaea survived the Byzantine restoration in Constantinople under Angevin protection; it was annexed to the Greek Despotate of the Morea in 1430. Achaea's former vassal, the Duchy of Athens was seized by mutinous Catalan mercenaries in 1311, and later by the Acciaioli, a Florentine banking dynasty, in 1388. Their final stronghold, Thebes fell to the Ottomans in 1460.^[422] Though the Ottomans challenged Venetian naval power, Venice held positions in the "Realm of Candia" into the early 18th century.^[423]

The State of the Teutonic Order originated c. 1225, when Duke Konrad I of Masovia offered Kulmerland in Prussia to the Knights. Within a decade, imperial, ducal and papal documents secured their right to rule the region and future conquests independently. In 1237, they gained Livonian lands through the merger with the Sword Brothers.^[424] After the Crusader states collapsed, the Order shifted its focus entirely to the Baltic, relocating the grand masters' headquarters to Malbork in 1309.^[425] To consolidate control, the Order attracted German nobles, burghers and peasants to the region by offering generous privileges.^[426] After Tannenberg, Polish invasions and internal conflict devastated Prussia, and by 1438 the grand master had lost influence over the leadership of the Order's Livonian branch.^[427] Prussia was transformed into a Protestant duchy in 1525, and Livonia in 1561.^[428]

The Hospitallers conquered the island of Rhodes from the Byzantines in 1306–1309.^[429] Though limited in size and resources, Rhodes was heavily fortified using income from the Hospitallers' overseas estates.^[430] The island resisted Mamluk and Ottoman invasions, but was taken by the Ottoman Sultan Suleiman II in 1522.^[431] In 1530, the Hospitallers received the Mediterranean islands of Malta and Gozo in fief from Emperor Charles V.^[432] They withstood the 1565 Great Siege of Malta, and only lost the islands to Napoleon Bonaparte in 1798.^[433]

The Turkoman destruction and desecration of Christian shrines was a central theme in Pope Urban's speech at Clermont. Following the capture of Bethlehem, Jerusalem, and Nazareth—three of Christendom's holiest sites—the Franks launched ambitious construction programs.^[434] The archaeologist Denys Pringle observes that a "coherent and distinctive" architectural style emerged in the Crusader states, shaped by widespread use of stone and scarcity of timber, resulting in flat, level structures.^[435] The most remarkable project was the reconstruction of the Church of the Holy Sepulchre, redesigned in the style of Western pilgrimage churches to incorporate the Aedicule, Calvary and Christ's Prison within a single complex.^[436] The Armenian Cathedral of Saint James in Jerusalem, completed in the 1160s, offers clear evidence of the fusion between local and Western architectural traditions.^[437] In coastal cities, multi-storey houses were built in the Western Mediterranean style with shops or loggias below and appartments above. Frankish settlers often lived in newly founded villages laid out in rectangular plans.^[438]

The development of western architecture is more clearly demonstrated in Cyprus, where the Saint Sophia Cathedral (now Selimiye Mosque) in Nicosia was built in early Gothic—though the roofs are terraced—and the façade of the Venetian governors' palace in Famagusta reflects the Renaissance. Under Frankish rule, urban eastern Christian churches also adopted Western styles.^[439] The impoverished Latin emperors had neither time nor resources for building projects in Constantinople. Elsewhere in Frankish Greece, monastic orders and nobles erected Gothic monasteries and rebuilt existing structures in Gothic style.^{[note 54]} Gothic influence on native architecture is visible in both Frankish Greece and Epirus.^{[note 55][442]} According to Christiansen, churches and other public buildings in Baltic towns served as "symbols of [an] imported culture", marked by simplicity and precision.^[443]

Figurative art in the three northern Crusader states now survives almost exclusively on coins,^{[note 56]} while the Kingdom of Jerusalem has yielded a far richer material record.^[445] These artefacts reveal the strong influence of Byzantine art,^[446] though the earliest surviving works in the Holy Sepulchre reflect a Western style.^{[note 57][447]} Both the Church of the Holy Sepulchre and the Church of the Nativity were decorated with mosaics in the mid-12th century.^[446][448] By this time, Western artists creating luxurious illuminated manuscripts at the Holy Sepulchre were also markedly influenced by Byzantine aesthetics.^[449] The earliest and most opulent example is the Melisende Psalter, commissioned by King Fulk for Queen Melisende c. 1135.^[450][451] Jotischky identifies the sponsorship of icons by Frankish donors as perhaps "the most remarkable evidence for Byzantine tastes in crusader arts". Surviving examples can primarily be found in Saint Catherine's Monastery on Mount Sinai and in Cyprus.^[452]

Few artefacts have survived from Frankish Greece, but a cycle of frescoes portraying Francis of Assisi still exists in the Kalenderhane Mosque in Istanbul.^[453] A monumental fresco depicting scenes from the Roman de Troie in a reception hall in Patras is known only from a late 14th-century travelogue, while another large wall painting, of Saints Anthony the Great and James, survives in a gatehouse at Acronauplia.^[454] In the Baltic, the celibate or endogamous ruling class rejected local traditions, maintaining a distincty Catholic and German culture.^[455]

The movement inspired what the medievalist Elizabeth Lapina describes as "an unusually large and varied body" of narrative sources, many authored by clergy. The earliest chronicles of the First Crusade represent the first attempt since antiquity to construct a comprehensive narrative of a military campaign.^[456] The Gesta Francorum ('Deeds of the Franks'), the earliest extant account, was completed by 1104. This text—or perhaps an earlier compilation—became the main source for later histories by Raymond of Aguilers, Fulcher of Chartres, and Robert of Rheims. Unlike these pro-papal writers, who cast Pope Urban as the crusade’s primary instigator, the German chronicler Albert of Aachen attributed the initiative to Peter the Hermit.^[457][458]

Though the First Crusade remained the most frequently chronicled event, later expeditions inspired new histories by authors such as Odo of Deuil, Otto of Freising, and Oliver of Paderborn.^[459][460] Whereas 11th-century crusade accounts were written in Latin, three chroniclers of the Fourth Crusade—Geoffrey of Villehardouin, Robert of Clari, and Henri de Valenciennes—composed in the vernacular, specifically Old French.^[461] Many chroniclers focused on individuals they admired.^{[note 58][462]}

The history of the states founded as a result of the crusades constitutes a separate branch of crusade literature. William of Tyre's chronicle, one of the earliest historical works translated from Latin into Old French, seeks to encourage the Franks of the Crusader states and raise crusading zeal in the West.^[464] The Chronicle of the Morea, a key source on Frankish Greece, survives in French, Greek, Aragonese, and Italian versions.^[465] In the Baltic, Henry of Livonia expressed sympathy for the Christianised natives in his Chronicle of Livonia, but the anonymous author of the Livonian Rhymed Chronicle praised the crusaders' violence.^[466] Several narrative texts are composed as prosimetra, integrating prose and verse.^[461]

Robert of Rheims's chronicle inspired several verses in the Song of Antioch, a French chanson de geste (epic poem) recounting the siege of Antioch.^[468] This poem initiated a semi-historical Crusade cycle of popular poems.^[469] By c. 1130, songs and hymns about the First Crusade were so widely performed in both Latin and the vernacular that the chronicler Guibert of Nogent noted he included nothing in his work that had not already been publicly sung.^[470] However, only 179 vernacular crusade songs have survived, the majority in Occitan and composed in traditional genres such as sirventes, pastorellas, and planhs.^[471] According to the literary historian Linda Paterson, the troubadour Marcabru composed "one of the most powerful ... Occitan hortatory songs" in praise of the Iberian crusades after the failure of the Second Crusade.^[472] Most French and Occitan crusade songs date from the time of the Third Crusade.^[473]

Though medieval Muslim scholars never treated the Crusades as a distinct subject, Muslim poets, such as Ibn al-Khayyat, warned fellow believers of the threat posed by the "polytheists" shortly after the First Crusade.^[474] Only two contemporary Muslim accounts of everyday interactions with Franks have survived: one by the Arab aristocrat Usama ibn Munqidh, and another by Ibn Jubayr, a pilgrim from Al-Andalus. Some medieval Arabic epic also reference the Crusades, including a popular tale of the warrior woman Dhat al-Himma and her triumph over a Frankish king, Malis.^[475] Byzantine vernacular literature borrowed popular themes, such as knights and love, from Western chivalric romances.^[476]

Opponents of the Gregorian Reform (such as the scholar Sigebert of Gembloux) condemned the concept of penitential warfare, but their voice lost in the euphoria raised by the successful First Crusade.^[477] The idea was also foreign to the Byzantines, and writers like Anna Komnene despised both the crusades and their participants.^[478] Mainstream Catholic criticism of crusading initially focused on certain aspects of the movement, like the risks of a crusader's absence from their home.^[479] The existence of military orders was unacceptable for those who regarded monastic life incompatible with knighthood.^[480] Millenarian thinkers, like Joachim of Fiore, regarded the crusades as phenomena of a passing period, stating that the Muslims' voluntary conversion to Christianity would introduce a new age sometime soon.^[481]

The geographical expansion of the crusades attracted a new wave of criticism because many thought that crusades against Christians in Europe distracted attention from the Holy Land.^{[note 59][479]} Some Occitan troubadours went as far as associating the northern French crusaders invading Occitania with the Muslims menacing the Holy Land.^[483] The complete failure of the crusades for the Holy Land after the mid-13th century prompted the chronicler Salimbene di Adam to state that attempts to recover the Palestinian holy places did not enjoy divine support. Others argued that the Christians were unable to overcome the Muslims in the Levant due to demographic disparity, or emphasised that the crusades prevented effective proselytism among Muslims. The Dominican friar Humbert of Romans compiled a whole study against similar arguments in 1274.^[484] Driven by despair, the troubadour Austorc d'Aorlhac and the Templar Ricaut Bonomel came close to blasphemy and apostasy in their lyrics.^[485]

From the beginning of the Reformation, anti-Catholic theologians criticized multiple aspects of the crusading movement.^[486] In his 1517 Ninety-five Theses, Martin Luther challenged the theology of indulgences and rejected papal authority by publicly burning the bull issued against him.^[487] He also denounced monastic vows and encouraged the Teutonic Knights to marry.^[488] Interpreting the Ottoman advance as divine punishment, Luther initially opposed anti-Ottoman crusades, but after the 1529 Siege of Vienna, he reversed his position and advocated a large-scale Christian campaign eastward.^[489] Likewise, the Catholic theologian Erasmus criticized both the preaching of crusade indulgences and priestly participation in military affairs, but supported the idea of a secular anti-Ottoman campaign.^[490]

Scholarly interpretations differ on how the crusading movement influenced interactions among Western, Islamic, and Orthodox cultures. While the campaigns caused significant suffering and heightened interreligious tensions, their violence was not exceptional by the standards of the time. The crusades' role in intercultural exchange remains unclear, as other factors—such as trade—also facilitated the spread of ideas and technologies. The sack of Constantinople severely damaged Catholic-Orthodox relations, undermining any effective cooperation against the Ottoman Empire.^[491]

The crusading movement expanded Western Christendom’s frontiers in Iberia and the Baltic, leading to the settlement of Catholic nobles and peasants, and the spread of the Catholic Church and a unified liturgy.^[492] While the Crusades failed to stop Ottoman expansion, they did slow it, with the final Ottoman incursion into Central Europe repelled by a crusading force. Even in the early 20th century, France and the United Kingdom invoked the Crusades to legitimise their territorial ambitions in the Middle East.^[493]

Throughout Western Europe, statutes, frescoes, and stained-glass windows were created to commemorate the crusades and their participants.^{[note 60]} Relics brought from crusades were often donated to local churches.^[495] During the Romantic era, artists frequently sought inspiration from medieval Crusade literature, as reflected in the 1830s decoration of five rooms with 120 paintings of Crusade scenes in the Palace of Versailles.^[496][497] The Crusades inspired writers, and major works such as La Gerusalemme liberata ('Jerusalem Delivered') by Torquato Tasso, in turn inspired others.^[498] Walter Scott's novels set during the Crusades, including Ivanhoe (1819) and The Talisman (1825), gained particular acclaim, with their historically inaccurate depictions of the past influencing artists and composers.^[499]

From a Western perspective, the first phase of Crusade historiography began with the earliest accounts of the First Crusade and extended to c. 1600, a period during which Catholic Europe faced persistent threats from Muslim powers. Medieval Catholic historians wrote from an irredentist viewpoint, presenting the reconquest of lost Christian territories as the driving force behind the Crusades.^{[note 61][500]} The second phase began in 1611 with Jacques Bongars's publication of primary sources, later consulted by Thomas Fuller, who completed a general history of the Crusades in 1639. During this period, scholarly works were strongly shaped by religious or secular ideologies. While the Protestant Fuller took a critical stance, the Jesuit historian Louis Maimbourg adopted a more sympathetic tone.^[501][502] The publication of sources continued,^[503] and scholarly language evolved: in the 18th century, neutral terms such as the German Kreuzzug, French croisade, and English crusade replaced the previously dominant "holy war".^[504] Enlightenment rationalism brought increased criticism, exemplified by Voltaire's reference to the "madness of the crusades" (1751).^[496][505]

The final phase began c. 1800 with the rise of nationalism and Romanticism, fostering a more favorable view of the crusading movement. This shift is exemplified by two monumental works: Friedrich Wilken's Geschichte der Kreuzzüge nach morgendländischen und abendländischen Berichten ('History of the Crusades from Eastern and Western Sources') and Joseph-François Michaud's Histoire des croisades ('The History of the Crusades'). In the 1830s, Leopold von Ranke introduced modern source criticism, which his student Heinrich von Sybel applied in his study of the First Crusade. The Société de l'Orient Latin ('Society of the Latin East'), founded in 1875, facilitated international scholarly collaboration on crusade research. Critical editions of primary sources laid the groundwork for two influential histories by René Grousset (1934–36) and Steven Runciman (1954). More recent comprehensive surveys include the six-volume Wisconsin Collaborative History of the Crusades (1955–89) and the Oxford Illustrated History of the Crusades volume (1995).^[506] Key debates in crusade studies concern the definition of crusades, the motives of participants, competing social models (such as colonialism and integration),^[507] and the critique of earlier Eurocentric scholarship.^[508] Muslim historians have generally shown limited interest in the Crusades, with the first Arabic account of the movement produced only in 1899 by the Egyptian historian Sayyid ʿAli al-Ḥarīrī.^[509][510]

• History of Christianity
• Religious violence
• Christianity and violence