TheCrusading movement—a major religious, political, and military endeavour of theMiddle Ages—is conventionally dated from theCouncil of Clermont (1095), at whichPope Urban II proclaimed an armed expedition in support ofEastern Christians underMuslim rule. He framed it as a form of penitentialpilgrimage. By then,papal authority had grown through church reforms, and tensions with secular rulers encouraged the notion ofholy war—combiningclassical just war theory,biblical precedents, andAugustine's teachings on legitimate violence. Armed pilgrimage aligned with the era'sChristocentric and militantCatholicism, sparking widespread enthusiasm. Western expansion was further enabled byeconomic growth, the decline of olderMediterranean powers, and Muslim disunity. These factors allowed crusaders to seize territory and found fourCrusader states in theLevant. Their defence inspired successiveCrusades, and thepapacy also launched crusading campaigns against other targets—Muslims inIberia,pagans in theBaltic, and other opponents of papal authority.

Though aimed primarily at the warrior elite through appeals tochivalric ideals, the movement depended on broad support fromclergy, townspeople, and peasants.Women, despite being discouraged, were involved as participants, proxies for absent crusaders, or victims. Although many crusaders were motivated byindulgences (remission ofsins), material gain also played a part. Crusading campaigns were typically initiated throughpapal bulls, with participants pledging to join by "taking thecross"—sewing a cross onto their garments. Failure to fulfilvows could result inexcommunication. Periodic waves of zeal produced unsanctioned "popular crusades".

The papal-sanctioned wars fostered distinctive institutions and ideologies. Initially funded through improvised means, later campaigns received more organized support viapapal taxes on clergy and the sale of indulgences. Core crusading forces were heavily armedknights, backed by infantry, local troops, and naval aid from maritime cities. Crusaders secured their holdings by building powerful castles, and the fusion of chivalric and monastic ideals led to the rise ofmilitary orders. The movement extendedWestern Christendom and created new frontier states, some surviving into theearly modern period. Crusading encouraged cultural exchange and left lasting marks on European art and literature. Despite a decline during theReformation, anti-Ottoman "holy leagues" sustained the tradition into the 18th century.

TheCrusades are commonly defined as Christianreligious wars waged by Western European warriors during theMiddle Ages to capture Jerusalem.^[1][2] Related campaigns differed markedly in spatial reach, temporal limits, and motivating aims.^[3][4] The wider crusading movement fostered distinctive institutions and ideologies that shaped society in Catholic Europe and neighbouring regions.^[5][6]

Inclassical antiquity,Greek philosophers andRoman jurists formulatedjust war theories that later influenced crusadingtheology.Aristotle stressed the need for a just end, asserting "war must be for the sake of peace".Roman law required acasus belli—just cause—and held that onlylegitimate authorities could declare war, with defence, restitution, and punishment considered acceptable grounds.^[7]

Although theBible—Christianity's core scripture—presents conflicting viewson violence,^{[note 1][9]} the 4th-centuryChristianisation of the Roman Empire gave rise to Christian just war theory. BishopAmbrose, a former imperial official, was the first to equate enemies of the Christian state with those of the Church.^[10][11]

The empire was divided in 395.^[12] Fifteen years later, thesack of the city of Rome ledAugustine—Ambrose's student—to writeThe City of God^[13] in which he argued that the Bible'sprohibition on killing did not apply to wars waged with divine approval.^[14] He held that 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 reflections were nearly forgotten after thefall of the Western Roman Empire in 476.^[10][16]

From the ruins of the Western empire,new Christian kingdoms emerged, largely ruled byGermanic 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 killingsinful and requiredpenance—typicallyfasting^[17]—forabsolution.^[18]

Meanwhile, theEastern Roman (Byzantine) Empire endured, though much of its territory, including Jerusalem, wasconquered by the rapidly expandingIslamic Caliphate by the mid-7th century.^[19][20]Islam's holiest text, theQuran, addressesjihad—struggle to spread and defend the faith.^{[note 2][22][23]} In the early 8th century, Muslim forces entered Europe,conquering much of theIberian Peninsula. Christiansunder Muslim rule had to pay a special tax, thejizya.^[24] As conquests stabilized, a threefold civilisational order emerged: a fragmented Western Europe, a weakened Byzantium, and an ascendant Islamic world.^[25]

Resistance to Muslim advance led to the creation of the smallKingdom of Asturias in north-western Iberia. Over time, this resistance evolved into an expansionist movement, regarded by locals as divinely sanctioned. In the 9th century, repeated invasions by non-Christian groups across Western Europe revived the notion ofholy war:^[15] conflict authorized by a spiritual leader, pursued for religious aims, and rewarded withsalvation.^[26]Leo IV was the firstpope to promise salvation in 846 to those defendingthe papal territories.^[27][28]

As warfare became constant, a new military class of mounted warriors emerged. Known asmilites in contemporary texts, they specialized in weapons like the heavy lance.^[29][30] To restrain their violence, church leaders launched thePeace of God movement.^[31][32] Ironically, efforts to curb bloodshed militarized the Church, as bishops increasingly raised armies to enforce the Peace.^[33]

With weak central authority, regional strongmen seized control ofparishes andabbeys, often appointing unfit clergy. Believers feared such irregularities invalidatedsacraments,^[34][35] heightening anxiety overdamnation.^[17][36] Sinners were expected toconfess and perform penance to be reconciled with the Church. Since penance could be burdensome, priests began offeringindulgences—commuting penance into acts like almsgiving orpilgrimage.^[37][38] Penitential journeys toPalestine, known as theHoly Land, held special value, as the region was associated withJesus's ministry^[39][40] and contained theChurch of the Holy Sepulchre, believed to markhis crucifixion andresurrection.^[41][42]

In an age of endemic violence, concern over damnation intensified, fostering reform movements within the Church, which was regarded as the channel through whichdivine grace was dispensed. In 910,Cluny Abbey's foundation charter set a precedent by grantingmonks the right tofreely elect their abbot. TheCluniac Reform spread rapidly, backed by aristocrats who valued the monks'prayers for their souls.^[43][44] Cluniac houses answered solely to papal authority.^[45][46]

The popes, viewed as the successors ofPeter the Apostle, claimedsupremacy over the Church, citing Jesus'spraise for his apostle.^[47] In reality, Roman noble familiescontrolled the papacy until EmperorHenry III entered Rome in 1053. He appointed clerics who launched theGregorian Reform for the "liberty of the church", banningsimony—the sale of church offices—and givingcardinals, senior clergy, the sole right toelect the pope.^[48][49] Andrew Latham, a scholar ofinternational relations, argues that the Gregorian Reform placed the Western Church in conflict with "a range of social forces within and beyond Christendom".^[50] By then, divisions in theology and liturgy between Western and Easternmainstream Christianity had deepened,^{[note 3]} leading tomutual excommunications in 1054 and the eventual split between the westernRoman Catholic and easternOrthodox Churches.^[51][52]

A spiritual revival took root as new monastic communities like theCarthusians andCistercians emerged and theRule of Saint Augustine spread amongsecular clergy.Christocentrism—a renewed focus on Christ's life and sufferings—also shaped the period, inspiring itinerant preachers.^[53]

Four major powers dominated the Mediterraneanc. 1000: theUmayyads inAl-Andalus (Muslim Spain), theFatimids in Egypt, theAbbasids (nominally) in the Middle East, and the Byzantine Empire in southeastern Europe andAnatolia. Within decades, all experienced serious crises, particularly in the east, where recurring droughts andcold waves triggered famine and instability.^[54][55] In contrast,climate change benefitted Western Europe, fuelling economic and population growth.^[56]

Weakened by internal conflict, Al-Andalus fractured intosmall states, vulnerable to Christian expansion—a process called theReconquista.^[57] In Egypt and Palestine, repeated failure of theNile's floods led to famine and interreligious tension. In 1009, the Fatimid caliphAl-Hakim ordered thedestruction of the Holy Sepulchre,^{[note 4][59]} though it was later rebuilt with Byzantine support.^[60] Meanwhile,Turkoman migrations fromCentral Asia destabilized the Middle East. The Turkoman chiefTughril I, of theSeljuk clan, seized Baghdad in 1055;^[61][62] his successor,Alp Arslan, defeated the Byzantines atManzikert in 1072, opening Anatolia to Turkoman settlement.^[63][64]

As traditional powers declined, Italian merchants gained control of Mediterranean trade.^[65] TheNormans, originating in northern France,conquered southern Italy and Sicily by 1091.^[66][67] Their expansion threatened papal interests, promptingPope Leo IX to launch a military campaign against them. Althoughhis campaign failed, he had promised absolution to its participants^[68][69]—a 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 5][72]} These ambitions often aligned with reformist popes, who granted absolution to those fighting Muslim powers in Sicily and Iberia.^{[note 6][74][73]} As these territories were once Christian, papal attention soon turned to Palestine.Pope Gregory VII proposed a campaign to reclaim Jerusalem in 1074, though it never materialized.^[75] Two years later, disputes over papal and royal authority ignited theInvestiture Controversy, reviving interest in just war theory.^[76][77]Anselm of Lucca, acanon lawyer, compiled Augustine's writings to argue that war aimed at preventing sin could be an act of love. The theologianBonizo of Sutri considered those who died in such warsmartyrs.^[76][78] These ideas shaped the belief that just warfare could serve as penance.^[79]

Revived interest in Augustine's teaching on legitimate violence provided the Western Church with an ideological framework for military engagement.^[74] By the late 11th century, amid heightened concern over sin, the papacy was well positioned to mobilize the warrior class's values.^[80]

Facing Turkoman incursions, the Byzantine emperorAlexios I Komnenos sought military aid fromPope Urban II in 1095. Seeing this as a chance to reassert papal authority, Urban called for a campaign against the Turkomans at theCouncil of Clermont, offering spiritual rewards to participants.^[81][82] 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, more than 20,000 poorly organized crusaders set off in what became thePeople's Crusade. Most perished orwere massacred en route.^[83][84] A second wave followed between August and October in that year, comprising at least 30,000 warriors and as many non-combatants, led by prominent aristocrats includingRaymond of Saint-Gilles,Bohemond of Taranto, andGodfrey of Bouillon.^[85][86] They advanced through fragmented Muslim-held territories and captured the cities ofEdessa,Antioch, and Jerusalem by July 1099.^[87][88]

The first crusaders consolidated their conquests into fourCrusader states:Edessa,Antioch,Jerusalem, andTripoli. Their defence prompted new campaigns,the first as early as 1101. Several expeditions, especially those led by monarchs, became numbered.^[89][90] These campaigns brought about near-continuous warfare in the region, drawing forces from across the wider world, including crusaders from Western Europe,slave soldiers from sub-Saharan Africa, andnomadic horsemen from theEurasian steppes.^[91]

Edessa's fall in 1144 to the Turkoman leaderZengi triggered theSecond Crusade, led byLouis VII of France andConrad III of Germany, which failedin 1148.^[92][93] Zengi's son,Nur al-Din, unified Muslim Syria and dismantled the Fatimid Caliphate. These lands came under the control ofSaladin, an ambitiousKurdish general. In 1187, he destroyed the Jerusalemite field armyat Hattin and captured most Crusader territory, including the city of Jerusalem.^[94][95]

The resulting crisis triggered theThird Crusade, led byEmperor Frederick I,Richard I of England, andPhilip II of France. Although Jerusalem remained under Muslim rule, the Crusader states endured, and theKingdom of Cyprus was founded on former Byzantine territory.^[96][97] Later Crusades focused on recovering Jerusalem, but theFourth was diverted by the Byzantine claimant,Alexios Angelos, leading to thesack of Constantinople and the creation of aLatin Empire in the Aegean in 1204.^[98][99] TheFifth Crusade against Egypt failed in 1217–21. TheSixth regained Jerusalem in 1229 through negotiations by the excommunicatedEmperor Frederick II, butthe city was sacked in 1244 byKhwarazmian raiders.^[100] Its loss promptedLouis IX of France to launch theSeventh Crusade in 1248, which endedin defeat.^[101]

After theMamluks supplanted theAyyubids—Saladin's family—as the dominant Muslim power in theLevant, SultansBaybars andQalawun waged systematic campaigns against the Crusader states. Louis IX mounted theEighth Crusade, but died in 1270. In 1291 Qalawun's sonKhalil seized the last Crusader strongholds in theHoly Land.^[102] Despite continued proposals to reclaim Jerusalem,^{[note 7]} efforts were hampered by events such as theHundred 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] TheFirst Lateran Council in 1123 officially equated campaigns against theMoors (Iberian Muslims) with Crusades.^[108][109] These papally-sanctioned campaigns drove Christian expansion, reducing Al-Andalus to theEmirate of Granada by 1248.^{[note 8][110]}

Some crusades emerged from conflict with pagan groups.^[112] In 1107–08,Saxon leaders referred to the pagan SlavicWends' territory as "Our Jerusalem", though anti-Wendish war was recognized asa crusade only in 1147. From then, northern German, Danish, Swedish, and Polish rulers launched papally sanctioned campaigns against Slavic,Baltic, andFinnic tribes—collectively termed as theNorthern Crusades. By the 1230s, leadership had passed to theTeutonic Order's warrior monks, who also launched attacks on the neighboring OrthodoxRus' principalities.^[113][114]

Crusading zeal also turnedagainst Christian foes of the papacy. "Political crusades" were launched against Emperor Frederick II, his heirs, and rebellious papalvassals.^{[note 9][116]} From 1209, Pope Innocent III targetedheretics—Christians who rejected Church doctrine^[117]—and Crusades were proclaimedafter 1261 against the restored Byzantine Empire.^[118]

Despite internal divisions, theReconquista continued, ending with theconquest of Granada byCastile andAragon in 1492.^[119][120] In the early 14th century,Preussenreise—seasonal anti-pagan raids in the Baltic—became a hallmark ofchivalric culture.^[121] The historian Eric Christiansen called these "an interminable crusade".^[122][123] In the Western Mediterranean, popes also proclaimed crusades against Christian enemies, includingAragon, andSicily. During theWestern Schism (1378–1417), rival popes called crusades against each other's supporters.^{[note 10][125][126]}

Extensive piracy in the Mediterranean revived anti-Muslim crusading in the mid-14th century.^{[note 11][128]} International campaigns targeted the risingOttoman Empire but failed to stop thefall of Constantinople in 1453.^[129] TheHussite Wars reignited anti-heretical crusades in 1420,^[130][131] and theReformation saw indulgences granted to Catholics fightingProtestants.^[132] Although the Reformation weakened papal authority, the papacy continued to promote crusades, helping form anti-Ottoman "holy leagues" well into the early 18th 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]

Initially seen as a unique eventprompted by divine intervention, the expanding movement soon required stronger legal foundations.^[137] TheDecretum Gratiani, an influential collection of church law, permitted warfarec. 1140—but only against heretics.[138]^[139] Within decades, jurists likeHuguccio extended this to Muslims, citing just intent, recovery of Christian lands, and retaliation for violence.^[139] Crusading campaigns outside the Holy Land were often justified by the perceived spiritual importance of those regions.^{[note 12][140]} The Northern Crusades, originally framed as defensive, soon focused on conversion,^[141] while Crusades against anti-papal Christians were portrayed as essential to safeguard the Holy Land.^[142] The sack of Constantinople was further justified by the murder of the legitimate emperor, Alexios IV, and by the schism with the papacy.^[143]

Soon after Clermont, thechroniclerGuibert of Nogent wrote that "God has instituted in our times holy wars" so that believers 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 13][145][82]} Pope Urban referred toremissio peccatorum ("remission of sins") in one letter, and in another promised absolution of all penance.^[146]

Peter Abelard,c. 1130, still sharply criticized grants of indulgence, but most later theologians accepted it.[147] TheFourth Lateran Council codified Crusade indulgences in 1215, declaring that "sins repented by heart and confessed with mouth" would be remitted. The theological basis was clarified with the emergence of the "Treasury of Merit" doctrine, drawing on themerits of Christ and the saints,c. 1230.[148]^[149] Occasionally, offenders of particular crimes—such as arsonists, violators of trade embargoes with Muslims, and assailants of clergy—were granted indulgence.^[150] Debate over the scope of the indulgence continued, withBonaventure arguing that indulgences did not apply to those dying before fulfilling their vow, andThomas Aquinas maintaining that penitent crusaders who confessed would attain salvation even if they died before departing.^[151]

Crusaders' motives are inherently difficult to determine. Although contemporary sources emphasize religious fervour, secular ambitions also played a role because holding conquests required sustained Western presence.^{[note 14]} Many participants enlisted for pay.^[153] Most saw no contradiction between piety and material gain, especiallybooty, as theOld Testament includes repeated references to spoils seized in divinely sanctioned wars.^[154][155] Some sought fame; others, as noted by the historian Jonathan Phillips, the appeal of long-distance travel.^[156] Some criminals escaped harsher punishment by taking the cross.^{[note 15][157]} The medievalist Andrew Jotischky suggests figures like the robber baronThomas of Marle saw crusading as an opportunity for unpunished violence.^[158]

Pope Urban directed his appeal at Clermont to the country's military elite.^[159] By then, themilites—once a broad category—had become a distinct warrior caste, though knighthood would not be fully equated with nobility until the late 12th century.^[160] Aristocrats valued visible piety, and crusading offered a new outlet for what Madden calls their "simple and sincere love of God".^[161]

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 allowed them to maintain their identity without jeopardizing salvation.^[162][163] Crusade rhetoric mirrored their values, invokingvassalage and honour.^[164] Preachers cast Christ as a feudal lord, summoning knights to defend his stolen patrimony asmilites Christi ("Christ's warriors").^{[note 16][166][152]}

Crusading decisions were often collective, made within noble households led by influential lords.^[167] Success brought prestige, and crusading kin could make participation a family tradition.^{[note 17][169]} Yet failure meant disgrace or financial ruin.^[170][171] Even in theLate Middle Ages, chivalric ideals fuelled two expeditions: the 1390Barbary Crusade and the 1396Crusade of Nicopolis.^[172]

Although violence conflicted with their vocation, clerics often joined crusades.^[173] At Clermont, BishopAdhemar of Le Puy was the first to vow the journey to Jerusalem.^[174] The Fourth Lateran Council explicitly permitted clerics to join for up to three years without forfeiting theirbenefices.^[175] Secular clergy typically served aschaplains or administrators;^[176][177] senior churchmen led troops.^{[note 18][177]} Influential prelates also helped initiate the Northern Crusades.^{[note 19][182]} Despite vows likestabilitas voci ("stability of place"), monks joined too.^[173][176] Cistercians andPremonstratensians even took up arms occasionally, especially in the Baltic.^{[note 20][184]}

Urban elites played a vital role in several crusades.^[185] Fleets from Genoa, Pisa, andVenice helped establish and secure the Crusader states,^{[note 21]} gaining in return commercial privileges and city quarters.^[187] The city ofLübeck supported the conquest of Prussia.^[188] Iberian towns owed military service under royal charters—often replaced by a special tax calledfonsadera.^[189]

During the Fourth Crusade, DogeEnrico Dandolo convinced fellow leaders tocapture Zadar, a Catholic city in Dalmatia, and later advocated the assault on Constantinople. After its sack, Venice gained control of severalAegean islands, establishing patrician-led lordships.^{[note 22][192][193]}Marino Sanudo Torsello, a Venetian writer, became a key crusading theorist in the early 14th century.^[194]

The historianChristopher 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, andsquires. They were typically young men of modest means who joined for pay.^[195]

Following Clermont, Pope Urban barred clergy from accepting vows from those unable to fight and annulled existing ones.^[196] Nonetheless, the People's Crusade consisted almost entirely of unarmed commoners,^[197] inspired by charismatics likePeter the Hermit.^[198] In the First Crusade's noble-led armies, the number of non-combatants nearly matched the number of fighters. The historianConor Kostick describes them as "a slice of European society on the march".^[199] Chroniclers likeRaymond of Aguilers called common crusaders aspauperes ("the poor or defenceless") and saw their presence as vital for divine favour.^[200] Unlike nobles, captured commoners were often tormented or killed rather than ransomed.^[201]

The People's Crusade and subsequent mass movements inspired by grassroots crusading zeal are collectively known aspopular crusades.^[202][203] These included the 1212Children's Crusade, led by two charismatic boys;^{[note 23]} the1251 and1320 Shepherds' Crusades, the former sparked by a letter allegedly from theVirgin Mary; and the 1309Crusade of the Poor. None reached the Holy Land, and both Shepherds' Crusades were forcibly disbanded.^[205][206] In 1456, a peasant Crusader army helped repel the Ottomans at theSiege of Belgrade. This success encouraged future efforts to mobilize peasants in anti-Ottoman crusades, butin 1514 a crusading peasant army in Hungary turned on their lords.^[207]

Except for the Mongols, the crusaders confronted familiar enemies, portrayed as aggressors and thus furnishing a just cause for war.^[208] Conquest and colonisation produced multi-ethnic societies.^[209] In Iberia and the Crusader states, relations with native populations broadly followed the pre-conquestdhimmi model, relegating non-Catholic ethno-religious groups to second-class status.^[210][211]

Muslim legal expertsdivided the world intoDar al-Islam (theMuslim world) andDar al-harb (non-Muslim lands). Border regions like Syria and Iberia becamejihad battlegrounds, attractingmilitary volunteers—mujahideen andghazis—from acrossDar al-Islam.^[212][213] Accounts of relations between Christians—both pilgrims and natives—and Muslims at all levels, from the authorities to ordinary locals, in the Holy Land on the eve of the Crusades vary.^{[note 24][214]} Sporadic attacks on pilgrims likely shaped perceptions of danger,^[217] though Asbridge highlights that interfaith violence mirrored broader political and social turmoil.^[218]

Western Christians often mislabelled Muslims as idol-worshippers or heretics.^{[note 25][220][221]} Untilc. 1110, massacres of Muslims in conquered towns were common.[note 26]^[223][224] Violence was presented as a response to the Muslim occupation of the holy places and the oppression of Christians.^[225]

Later, crusaders rarely sought conversions, instead levying a poll tax akin to thejizya.^[226] Church law imposed various restrictions on Muslims, though enforcement is poorly documented.^{[note 27][227]} In the Crusader states, most Muslims—Arabic-speaking farmers—lived in self-governed communities underIslamic law.^[228] In Iberia,mudejares—Muslims under Christian rule—also faced second-class status.^{[229][230][231]}

Initially, few Muslims perceived the Crusades' religious character, and longstanding conflicts among Muslim rulers persisted. The Damascene scholaral-Sulami was the first to situate them within broader "Frankish", or Westerner, expansion.^[23][232] He interpreted their success as divine punishment for neglectingjihad.^[233] Zengi was among the era's first Muslim leaders receivingjihadist honours. Later rulers likewise invoked religious motives in anti-Frankish campaigns.^[234] In Iberia, theAlmoravids and theAlmohads strongly supportedjihad.^[235] Nonetheless, pragmatic Christian–Muslim alliances remained common throughout the period.^{[note 28][239][240]}

The liberation of eastern Christians was proclaimed a central aim of the First Crusade, yet early encounters proved disappointing.^[242] Emperor Alexios, expecting disciplined mercenaries or manageable allies, was unsettled by the crusaders' influx. He secured oaths for the return of reconquered Byzantine lands, but Bohemond retained Antioch, a former Byzantine provincial capital.^[242][243] Soon after Antioch's capture, Crusader leaders described local Christians as "heretics" in a letter to Pope Urban.^[216] In the Crusader states, Eastern Christians paid a poll tax, signalling their subordinate status, although their self-governance was reinforced^[244] and some retained considerable landholdings.^[245]

Orthodox Christians, orMelkites, formed the majority of Palestine's native Christian population and were also prominent in northern Syria.^[246] Catholic theologians regarded them asschismatics rather than heretics. Although most Orthodox bishops had fled Palestine before 1099, scattered references suggest the presence of an Orthodox hierarchy under Frankish rule.^{[note 29][248]} Monasticism experienced a revival under Byzantine patronage.^[249]

Certain Eastern Christian communities were treated as heretics for rejecting theCouncil of Chalcedon, whose teaching on Christ's twonatures (divine and human) was central to both Catholic and Orthodox theology.^[250][251] Among them, theArmenians—concentrated in northern Syria andCilicia^[252]—maintained autonomous lordships.^[253] Many welcomed the crusaders, and Armenian aristocrats formed marriage alliances with them. This cooperation led to a tenuouschurch union with Rome (1198)^[254] and ultimately to the FrankishLusignans' rule overCilician Armenia.^[255]Syriac (or Jacobite) Christians, mainly rural and Arabic-speaking, were viewed with suspicion and condescension;^[253] yet the Jacobite patriarchMichael the Syrian praised Frankish religious tolerance contrasting it with Byzantine policy.^[256] Another distinct group, theMaronites ofMount Lebanon, entered into communion with Rome, forming the firstEastern Rite Catholic Church in 1181.^[257]

Byzantine–Frankish relations were variable.^[258] Following the Fourth Crusade, Byzantine successor states likeEpirus andNicaea led resistance against the conquerors, although temporary Greek–Frankish alliances were not uncommon.^{[note 30][260]} InFrankish Greece, many Greekárchontes (aristocrats) retained lands and fought alongside Franks. Peasants suffered harsher conditions than under Byzantine rule.^[261] Orthodox bishops refusing papal supremacy were replaced by Catholic appointees, but Greek monasteries received papal protection.^[262] Latin conquest reinforced Orthodox identity, and persistent local resistance ultimately thwarted attempts to church reunification.^{[note 31][264]}

In northeastern Europe, Catholic and Orthodox churches coexisted in major trade centres, and the schism did not impede dynastic intermarriage. Catholic missionary activity only intensified after the Fourth Crusade. Despite occasional alliances between crusaders andRus' leaders, lasting control over Rus' lands was never achieved.^[265]

Trade in raw materials andslaves had long connected Christian and pagan communities in theBaltic region, although rivalry over trade routes often sparked armed conflict.^[266] Fromc. 1100, intensifiedGerman colonisation and unequal access to resources triggered more frequent clashes between the Wends and their Christian neighbours.^[267][268] In 1146, while promoting the Second Crusade, the Cistercian abbotBernard of Clairvaux encountered Saxon reluctance to abandon anti-Wendish campaigns. Adopting their perspective, he convincedPope Eugenius III to proclaim the Wendish Crusade.^[269][270] The Wends' structured society—with principalities, towns, and a priestly hierarchy—eased their eventual integration into Christendom.^{[note 32][273]}

Further east, theOld Prussians,Latvians, andCuronians had long resistedChristianisation. They lived in rural communities led by strongmen who thrived on trade and raiding.^[274] Crusaders employed coercion, bribery, and promises of protection to gain converts among them.^[275]Papal legates sought to protect the converts from exploitation but achieved little.^{[note 33][276]}

TheLithuanians, largely taxpaying peasants undernative lords, unified in the 13th century under Grand PrinceMindaugas. Baptized in 1253, he received a royal crown fromPope Innocent IV but later reverted to paganism.^[278] In 1386, Grand PrinceJogaila married QueenJadwiga of Poland. The subsequentmass conversion of Lithuanians to Catholicism eroded the Teutonic Knights' justification for crusade. In 1410, Polish-Lithuanian forces decisively defeated the Knights in theBattle of Grunwald. ThePreussenreise waned, with the last non-German crusaders entering the Baltic in 1413.^[279][280]

In the eastern Baltic, Finnic peoples lived in small rural communities, sustained by farming, slave-raiding, and fur-hunting.^[281] Legend has it thatEric IX of Sweden led acrusade to Finland in the 1150s, but the earliest confirmed expedition was authorized byPope Gregory IX in 1237.^[282][283] Danish crusaders conqueredEstonia in 1219, but by mid-century, German knights andburghers dominated the region's politics.^[284]

The Gregorian Reform did not satisfy those seeking a purer, simpler Christianity.^[285]Increased trade carrieddualist ideologies westward, distinguishing between an incorruptible God and an evilcreator of the material world. In Western Europe, their adherents became known asCathars or Albigensians.^[286] As Catholic churchmen saw heresy as a fundamental threat to the faith and to salvation,^[110] theThird Lateran Council granted indulgences, in 1179, to those who fought heretics.^[287] Yet, in southern France, Cathars were deeply embedded inOccitan society, and local elites were unwilling to act against heretical friends or kin.^[288]

In 1207, Pope Innocent III urgedRaymond VI, Count of Toulouse, to eradicate heresy. His reluctance or inability to comply led to excommunication by the papal legatePeter of Castelnau, who was soon murdered. In response, Innocent declared the firstAlbigensian Crusade.^[289][290] Northern French crusaders invaded Occitania, committing atrocities against both Cathars and Catholics.^{[note 34][292]} Though the campaigns strengthened French influence, they failed to eliminate heresy. That was eventually achieved bymendicant friars,inquisitors and secular authorities.^[293]

TheStedinger Crusade in northern Germany targeted peasants accused of heresy for refusing to pay thetithe (church tax).^[294] Hungarian rulers ledtwo failed crusades intoBosnia, allegedly home to a Catharantipope.^[295] In contrast, the radicalApostolici in northern Italy were swiftly crushed by crusading forces.^[296]

In 1206, Temüjin was proclaimedGenghis Khan, uniting the Mongol tribes under the belief in adivine destiny to conquer the world.^[297] Western Europeans first learned of theearliest Mongol conquests during the Fifth Crusade.^[298] As some tribes followed theEastern Syriac (Nestorian) Church, the Mongols came to be linked in Western thought to the people of the mythical Christian rulerPrester John, prompting hopes of an anti-Muslim alliance.^[299][300] However, theMongol invasion of Eastern and Central Europe in 1239–42 shocked Western Christendom. Although Pope Gregory IX called for a crusade, the Mongols withdrew from Europe following the death ofÖgedei Khan, Genghis's successor, in 1242.^[301][302]

In the Middle East, Mongol forcessacked Baghdad and destroyed the Abbasid Caliphate in 1258. Seeking protection,Hethum I of Cilician Armenia andBohemond VI of Antioch submitted toHulegu, the Mongolil khan (ruler of the Middle East). TheIlkhanate's expansion ended in 1260 when Mamluk forces defeated Hulegu's army in theBattle of Ain Jalut.^[303]

Roman legislation underConstantine the Great, the first Christian emperor, and Augustine's theology shaped Western Christian views ofJudaism. Constantineupheld Judaism's legality but imposed restrictions on its practitioners; Augustine asserted that Jews were divinely preserved yet punished withdispersion for rejecting Jesus.^[304]

Jewish migration to Western Europe coincided with the pre-Crusade economic boom.^[305] Coming from developed Islamic economies, Jewish merchants brought advanced commercial expertise. Free from canon law's anti-usury rules, they came to dominate moneylending, fuellingantisemitism.^[306] Local rulers valued Jewish economic contributions and offered protection, though often fragile.^[305]

Organized pogroms beganin the Rhineland during the First Crusade, reportedly driven by vengeancefor Christ's death and desire for Jewish property.^[307][308] In Jerusalem, crusaders massacred Jews,^[309] though communities in other towns—such asTyre andAscalon—survived.Jewish pilgrimage to the Holy Land intensified, with hundreds ofwestern Jews settling there during the Crusades era.^[310] AlthoughPope Calixtus II's bullSicut Iudeis forbade violence against Jews, crusade preaching repeatedly incited antisemitic pogroms.^{[311][312][313]}

Women were involved in the crusading movement from the outset.^[314] Though popes discouraged female participation, women always accompanied the armies as servants.^[315]Washerwomen received special papal approval early on.^[316] Women needed permission from a father or husband to join a crusade, whereas men, from 1209, could go without their wives' consent.^[317]

Gender bias prevailed on all sides.^[318] Christian chroniclers highlighted women's supportive roles—delivering water or stone missiles—but rarely mentioned female fighters.^[319] Muslim and Byzantine writers, in contrast, often depicted armed Crusader women as symbols of barbarity.^[320] Muslim sources also condemned the freedoms women enjoyed in Frankish societies.^[321] Crusaders were expected to abstain from sex; and women, both wives and sex-workers, were often expelled before major battles.^[322][315] Occasionally, high-ranking women led troops or conducted key diplomatic negotiations.^{[note 35][317]}

Women left behind were vulnerable to abuse by kin or neighbours.^{[note 36]} Some crusaders made formal arrangements with relatives or religious institutions to protect their wives and daughters; others entrusted wives or mothers with managing their estates.^{[note 37][326]} Raids by both Christian and Muslim forces frequently targeted women. After battles or sieges, victors often captured enemy women and children.^[327] The First Crusade was exceptional: crusaders often massacred entire populations of captured towns.^[328] In the Baltic, theLivonian Rhymed Chronicle praised the slaughter of pagan women and children as divinely sanctioned.^[329]Rape of captured women both by crusaders and their enemies was common.^[330][331] Noblewomen were typically ransomed, albeit for less than men of the same rank; other women were enslaved or forced into marriage.^[332]

High male mortality in the Crusader states meant that women often inherited fiefs, though they were expected to marry.^[333] Some inherited thrones: between 1186 and 1228, for example, four queens ruled Jerusalem.^{[note 38][336]} In Frankish Greece, the wives ofAchaean barons captured at theBattle of Pelagonia formed the "Parliament of Dames" in 1261 to negotiate peace with the Byzantines.^[337]

Tyerman notes that crusading "paraded across society in recruitment, funding and social rituals of support". The movement was accompanied byprocessions, priestly blessings, charity, and was also commemorated in works of art.^[338]

Crusades were typically proclaimed by the pope in his capacity asVicar of Christ.^[339]Crusade bulls articulated the aims, urged participation, and detailed spiritual and temporal rewards;^{[note 39][340][341]} they were read in all Catholic churches fromPope Alexander III's time.^[342] Pope Gregory IX authorized theDominicans to preach Baltic crusades without further approval,^[343] a privilege later extended to theFranciscans and Teutonic clergy.^[344]

Crusades were promoted by clerics. Papal legates addressed nobles at major assemblies. Village and town preaching was unstructured until Pope Innocent III coordinated propaganda through local committees, though subsequent popes preferred less formal methods. From the early 13th century, mendicant friars assumed responsibility for preaching. By the century's end, many used manuals by propagandists likeHumbert of Romans.^[346] Crusade-promotional sermons often began withmoral anecdotes.^[347]

Crusaders took public vows, usually followed by a ceremony where a cloth or silk cross—typically red—was sewn onto their cloak. By "taking the cross", they pledged themselves toChrist's call in theGospel of Matthew: "If any man will come after me, let him … take up his cross and follow me".^[348][349] The ceremony resonated with the 11th-centuryimitatio Christi ("imitation of Christ") spiritual movement, which encouraged believers to follow Christ's example by serving others.^[53] Pilgrim emblems like a staff and a pouch were often also distributed.^[350] The cross had to be worn by crusaders until their return; premature removal was sanctioned by church authorities,^{[note 40][352]} with rare exceptions like illness, poverty, or incapacity.^[353] By the late 12th century, crusaders were widely known ascrucesignati ("signed with the cross").^[354]

As penitents and armed pilgrims, crusaders were classed in canon law as provisional clerics under ecclesiastical jurisdiction.^[339] Their early secular privileges are poorly documented. According to acollection of canon law, First Crusaders and their goods were "under the Truce of God". Guibert of Nogent notes that Pope Urban offered protection to crusaders and their households, with excommunication prescribed for offenders.^[355] This legal approach was still described as "new" in 1107 by the canonistIvo of Chartres, who was reluctant to adjudicate a case concerning the capture of a crusader's fortification.^{[note 41][357]} The First Lateran Council formalized it, protecting the crusaders' "houses and households" and orderinglatae sententiae or automatic excommunication for infractions, but enforcement was inconsistent.^[358] Pope Eugenius III also suspended lawsuits against crusaders and interest payment on their debts,^[359][360] and authorised them to sell land—including fiefs—without the consent of family members or lords.^[361]

The historian Simon Lloyd notes that crusading was "crippingly expensive". Although precise figures are mainly lacking,[note 42]^[362] estimates suggest that a knight spent over four years' income.^[363] Aristocrats sold commodities or granted civic privileges for cash.^{[note 43]} Inherited lands were often mortgaged or pledged viavifgage, allowing creditors repayment from property income. Others secured funds through gifts or loans from kin or lords.^{[note 44][366]} In Iberia,parias (tributes from Muslim rulers) helped fund Christian forces.^[367]

An extraordinary tax for Holy Land defence was first introduced in France and England in 1166. The 1188 "Saladin tithe" imposed a ten percent levy on income and property, thoughcompliance varied.^[368] In 1199, Pope Innocent III orderedchurch revenues taxed for crusading.Pope Gregory X defined collection procedures in 1274, but clergy often resisted.^[369][370]

From 1199, donations were gathered viachurch chests.^[371] In 1213, Innocent III introduced a new mechanism, allowing anyone—except monks—to vow a crusade and redeem it financially.^[372][373] This practice of purchasing indulgences continued into the early modern period.^{[note 45]} With the spread of printing in the mid-15th century, indulgence sheets were mass-produced with blanks for beneficiaries' names.^[374]

The historian Peter Lock notes that mounting "a crusade was no easy task and the time given for preparation was often short". The gathering of pack animals, wagons, war horses, and supplies, like fodder and water, was essential in individual crusades' success, but is poorly documented in contemporary sources.^[375]

Command during most crusades was divided and uncertain, with desertion common.^[376] Morale was often sustained byvisions, processions, andrelics.^{[note 46][377][378]} Most crusaders lacked experience in urban sieges, which were typical of Levantine warfare.^[379] Crusaders generally avoidedpitched battles in which defeat risked catastrophic losses.^{[note 47][380]} Siege warfare usedtrebuchets,towers, andbattering rams. Muslim defenders employedGreek fire, countered by crusaders with vinegar-soakedhides.^[383] From the late 13th century, strategic planning for Holy Land campaigns distinguished between an initial campaign (passagium particulare) to secure a foothold and the full-scalepassagium generale.^[103]

Heavily armoured knights formed the Crusader armies' backbone.^[384] The historian John France calls them the "masters of close-quarter warfare". In the east, they primarily confronted mounted archers and relied on infantry, particularly bowmen and spearmen, for support.^[385] Franks also employed native light cavalry, orTurcopoles, to harass enemy troops.^[386] In the north, Teutonic Knights deployed converted Prussians for raids on pagan settlements.^[387] Spanishalmogavars—agile raiders—fought with daggers, short lances, anddarts.^[189]

Naval support came mainly from Italian city-states and the Byzantines in the Levant. Egypt maintained the sole Muslim fleet in the region, but its small vessels posed little threat to Western dominance. After Emperor Frederick I's failed overland expedition, major Levantine crusades were done by sea.^[388] In the north, large Christian merchant ships, carrying up to 500 people, easily outmatched Baltic long-ships and raiding vessels.^[389]

Throughout conquered territories, castles served military and administrative functions, merging Western and local designs. In the Levant, early Norman-style towers gave way to the localcastra layout of walled courtyards, which evolved into concentric castles with layered defences.^{[note 48][391][392]}Spur castles on rocky hills, with towers and a keep, represent—according to Phillips—"the most spectacular examples of Frankish military architecture".^{[note 49][393]} In Iberia, over 2,000 castles were raised along frontiers.^[394] The Teutonic Knights first built timberblockhouses in the Baltic, but byc. 1250 switched to stone, then brick for its availability and lower cost.[395]

Tyerman argues that themilitary orders were "crusading's most original contribution to the institutions of medieval Christendom". Thesereligious communities followedmonastic rules but were committed to armed defence of Christianity.^[396][397] The first emerged when the French nobleHugues de Payens and fellow knights pledged to protect pilgrims in the Holy Land. Taking themonastic vows of chastity, poverty, and obedience in 1119, they formed a confraternity. They became known as theKnights Templar after their headquarters in the formerAl-Aqsa Mosque, associated with theTemple of Solomon.^[398][399]

The idea of warrior-monks aligned with contemporary chivalric and ecclesiastical ideals.^[400] Byc. 1130, Bernard of Clairvaux praised the Templars as a "new knighthood".[401] Their model inspired other groups, especially in borderlands of Latin Christianity.^[402] In the Holy Land, nursing confraternities became militarized, giving rise to orders such as theKnights Hospitaller, and the Teutonic Knights.^[403][402] In Iberia, royal patronage supported orders, such asCalatrava, andAviz. In the Baltic, bishops founded the Sword Brothers and theOrder of Dobrzyń, both later absorbed by the Teutonic Order.^[404][405]

Military orders were structured by function: knight-brothers andservientes (military servants) fought; priest-brothers provided spiritual care; nobles could temporarily join for spiritual rewards.^[406] The Templars and Hospitallers grew into transnational institutions, led by electedgrand masters and owning estates throughout Western Christendom.^[407][408] Their convent networks facilitated the flow of goods and cash.^[409]

The orders were occasionally criticized for greed, pride, or adopting non-Christian customs.^[410] After the Crusader states fell, criticism increased because many orders lost their justification for existence. The Templars, focused solely on fighting, faced intense scrutiny.^[411] In 1307,Philip IV of France orderedtheir mass arrest on charges ofapostasy, idolatry, andsodomy. Despite the lack of physical evidence, the Order was dissolved at theCouncil of Vienne in 1312.^[412] The Hospitallers endured but shifted focus to naval defence in the Mediterranean. In Iberia, the military orders gradually secularized, aligning with the crown of Spain and Portugal. The Teutonic Knights survived the Reformation underHabsburg leadership in Germany.^[413]

The crusading movement fostered the creation of new states on the fringes of Latin Christendom. The historianRobert Bartlett describes them as "autonomous replicas, not dependencies, of western and central European polities".^[414]

The four Crusader states established Catholic rule in the Levant[415] and strengthened commercial links between the region and Catholic Europe.^[416] Their limited economic surpluses were directed chiefly towards military needs.^[417] Edessa, the weakest, fell to Zengi after a failed attempt to ally with his Muslim rivals, theArtuqids.^[415] Internal strife undermined Jerusalem, leaving it vulnerable to Saladin's conquest, though the Third Crusade regained much of the coast. Antioch and Tripoli entered union aftera succession war.^[418] After Frederick II's crusade, the kings of Jerusalem were mostly absent, and the kingdom was ruled by regents, sometimes appointed by their opponents.^[419] By the Mamluk advance, the Crusader states had fragmented into competing lordships andcommunes.^[420]

Cyprus, a day's sail from Syria, was a vital crusading base.^[421] From 1269, its Lusignan kings claimed Jerusalem, although theSicilian Angevins contested this from 1277.^[422] TheBlack Death and shifting trade routes led to declinec. 1350. A CypriotCrusade on Alexandria provoked Genoese reprisals, leading to the sack of the main port of Cyprus,Famagusta. After the Lusignan dynasty ended in 1474, the islandpassed to Venice.^[423]

Months before the sack of Constantinople, the leaders of the Fourth Crusade agreed topartition the Byzantine Empire: an elected emperor would receive a quarter, the rest go to other Frankish leaders and Venice.^[424][425] Trade in wheat, olive oil and silk enriched the lords of thePeloponnese, making Achaea a centre of chivalric life.^[426][427] It survivedunder Angevin protection until annexed by theDespotate of the Morea in 1430.Athens, initially an Achaean vassal, changed hands before falling to the Ottomans in 1460.^[428] DespiteOttoman pressure, Venice retained parts of its Aegean lands into the 18th century.^[429]

The Teutonic Order was grantedKulmerland in Prussia by the Polish dukeKonrad I of Masovia in the 1220s, soon gaining autonomy over future conquests. In 1237, the Teutonic Knights seized Livonia through merger with the Sword Brothers.^[430] The Order attracted German settlers with land and privileges, but Polish incursions andinternal strife weakened its control after the Battle of Grunwald.^[431]Prussia became a Protestant duchy in 1525,Livonia in 1561.^[432]

The Hospitallers captured the island ofRhodes from the Byzantines in 1306–1309.^[433] Despite its strong fortifications and earlier resistance to Mamluk and Ottoman assaults, Rhodes wastaken by SultanSuleiman II in 1522.^[434][435] In 1530, EmperorCharles V granted the Hospitallers the islands ofMalta andGozo.^[436] They withstood the 1565Great Siege of Malta, but lost the islands toNapoleon Bonaparte in 1798.^[437]

Opponents of the Gregorian Reform, such asSigebert of Gembloux, condemned penitential warfare, but their voice was lost in the euphoria following the First Crusade.^[438] The concept was equally alien to Byzantines; PrincessAnna Komnene openly scorned the Crusades and their participants.^[439] Mainstream Catholic criticism targeted specific aspects such as the risks posed by crusaders' absences.^[440] The rise of military orders also drew objections from those who viewed monasticism as incompatible with knighthood.^[441]Millenarian thinkers likeJoachim of Fiore saw the Crusades as transient, predicting the Muslims' voluntary conversion.^[442]

As the Crusades spread geographically, criticism intensified, especially over campaigns against Christians.^{[note 50][440]} Some Occitantroubadours even equated anti-heretic crusaders with Muslim foes.^[444] The Levantine crusades' failure prompted the chroniclerSalimbene di Adam to conclude they lacked divine support.^[440] Driven by despair, the troubadourAustorc d'Aorlhac and the TemplarRicaut Bonomel approached apostasy in their lyrics.^[445] In 1274, Humbert of Romans produced a full rebuttal to anti-Crusade critics.^[446]

From the Reformation, anti-Catholic theologians attacked crusading.^[447]Martin Luther denounced indulgences and papal authority.^[448] The Catholic theologianErasmus also criticized indulgence preaching and clerical involvement in warfare.^[449]

The destruction of Christian shrines by the Turkomans featured prominently in Pope Urban's speech at Clermont. After capturingBethlehem, Jerusalem, andNazareth—three of Christendom's holiest sites—the Franks launched ambitious construction programmes.^[451] The archaeologistDenys Pringle observes that a "coherent and distinctive" architectural style emerged, shaped by the abundance of stone, scarcity of timber, and preference for flat-roofed designs.^[452] The medievalist Steve Tibble terms it the "architecture of fear", characterised by the use of heavy timber bolts, and windows secured with iron bars.^[453]

The most remarkable project was the rebuilding of the Church of the Holy Sepulchre, redesigned in the style of Western pilgrimage churches to enclose theAedicule,Calvary, and Christ's Prison within one complex.^[454] The fusion of local and Western architectural traditions is well illustrated by the ArmenianCathedral of Saint James.^[455] Coastal towns had multi-storey houses with shops or loggias below and residences above. Frankish settlers often lived in newly founded villages laid out in rectangular plans.^[456]

Western architectural development is especially visible in Cyprus. The Saint Sophia Cathedral inNicosia (nowSelimiye Mosque) was built inearly Gothic, though with terraced roofs. TheVenetian governors' palace in Famagusta features aRenaissance façade. Urban eastern Christian churches also adopted Western styles.^[457] In Frankish Greece, monastic orders and nobles erected Gothic monasteries and rebuilt existing buildings in Gothic style,^{[note 51][459]} In the Baltic, public buildings reflected Western styles, characterized by simplicity and precision.^[460]

In the three northern Crusader states,figurative art survives almost solely on coinage,^{[note 52]} whereas Jerusalem left a much richer artistic legacy.^[462] These artefacts reveal significantByzantine influence,^[463] although the earliest surviving decorations exhibit Western stylistic features.^{[note 53][464]} By the mid-12th century, both the Holy Sepulchre and theChurch of the Nativity were decorated with mosaics.^[463][465] Western artists working on illuminated manuscripts in Jerusalem also embraced Byzantine aesthetics.^[466] The finest example is theMelisende Psalter, commissioned byKing Fulk forQueen Melisendec. 1135.[467]^[468] Jotischky describes Frankish sponsorship oficons as perhaps the clearest sign of "Byzantine tastes in crusader arts", with surviving works primarily housed inSaint Catherine's Monastery onMount Sinai and in Cyprus.^[469]

From Frankish Greece, little remains. A cycle of frescoes portrayingFrancis of Assisi survives in Istanbul'sKalenderhane Mosque,^[470] and a wall painting of SaintsAnthony andJames in a gatehouse atAcronauplia.^[471] In the Baltic, thecelibate orendogamous elites rejected local traditions, preserving a distinctly Catholic and German culture.^[472]

Coinciding with the "Twelfth-Century Renaissance", the movement inspired a remarkable range of literary works,^[473] including what historian Elizabeth Lapina describes as "an unusually large and varied body" of narrative sources.^[474]

Early accounts of the First Crusade revived the tradition of comprehensive military history last seen in antiquity.^[475] TheDeeds of the Franks, completed by 1104, became the basis for later accounts by Raymond of Aguilers,Fulcher of Chartres, andRobert of Rheims. These pro-papal writers portrayed Pope Urban as the key instigator, although the German chroniclerAlbert of Aachen credited Peter the Hermit.^[476][477]

Although the First Crusade remained the most extensively recorded, subsequent expeditions inspired new works byOdo of Deuil,Otto of Freising, andOliver of Paderborn.^[478][479] Whereas early narratives were in Latin, three chroniclers of the Fourth Crusade—Geoffrey of Villehardouin,Robert of Clari, andHenri de Valenciennes—wrote inOld French.^[480] Many chroniclers focused on individual crusaders.^{[note 54][481]} Several authors blendedprose andverse in the hybridprosimetra form.^[480]

A distinct literary genre emerged around the Crusader states.William of Tyre's chronicle sought to rally Western support and sustain Frankish morale.^[483] TheChronicle of the Morea, central to Frankish Greece's history, survives in French, Greek, Aragonese, and Italian.^[484] In the Baltic, the chroniclerHenry of Livonia sympathized with Christianized natives, whereas theLivonian Rhymed Chronicle glorified Crusader brutality.^[485]

Robert of Rheims's chronicle inspired verses in theSong of Antioch, a Frenchepic poem recounting Antioch's siege.^[487] This work launched a semi-historicalcycle of Crusade epics.^[488] Only 179 vernacular songs survive, mostly inOccitan by troubadours, using traditional forms likesirventes,pastorellas, andplanhs.^[489] The literary scholar Linda Paterson highlights the OccitanMarcabru's praise of the Iberian crusades as especially powerful.^[490] Most French and Occitan songs date to the Third Crusade.^[491] In Iberia, the SpanishSong of My Cid recounts the exploits of the Castilian nobleRodrigo Díaz de Vivar.^[492][493]

Though medieval Muslim scholars never treated the Crusades as a distinct subject, Muslim poets like Ibn al-Khayyat warned of the threat of the "polytheists".^[494] Only two Muslim texts record daily contact with Franks: the aristocratUsama ibn Munqidh's memoir andIbn Jubayr's pilgrimage account. Some Arabic epics—such as the tale of the warrior womanDhat al-Himma—also reference the crusades.^[495]

After the First Crusade, Byzantine writers increasingly treated Western Europeans as a single group, using terms such asLatini.Niketas Choniates and other chroniclers acknowledged Latin military skill but depicted them as barbarians.^[496] During the Second Crusade, clashes inspired two poems likening crusaders to wild beasts.^[497] Later, Byzantine vernacular literature absorbed motifs—knights, love, and adventure—from chivalric romance.^[498]

The earliest Armenian reference to the Crusades—a 1098colophon to a legal text—speaks of the arrival of "the western nation of heroes". Chroniclers such asMatthew of Edessa cast the Crusades in apocalyptic terms, associating Frankish rule with the fourth kingdom inDaniel's prophecy.^[499] In 1144, the prelateNerses Shnorhali composed aLament for the Fall of Edessa, voicing hope for Islam's future downfall.^[500] The Cilician nobleSmbat'sChronicle shows familiarity with Western customs.^[501]

The Rhineland massacres sparked a literary response unprecedented in European Jewish history. TheMainz Anonymous, one of the earliest Hebrew accounts, inspired subsequent chronicles, includingEliezer ben Nathan's.^[502]Laments commemorating the pogroms entered theNinth of Av liturgyc. 1200.[503] Jewish pilgrims such asBenjamin of Tudela recorded their journey in travelogues,^[504] and an unknown Jew from France who settled in the Holy Land in 1211 wrote a treatise urging others to reclaim it for Judaism.^[505]

Scholars disagree on how the movement shaped interfaith relations. Although the campaigns caused suffering and deepened religious tensions, their violence was typical for the era. The Crusades' impact on intercultural exchange remains uncertain, as trade and other channels also transmitted ideas and technologies. The Sack of Constantinople severely damaged Catholic–Orthodox relations, hindering cooperation against the Ottomans.^[506] Even so, the Crusades delayed Ottoman expansion, and a final Ottoman push into Central Europe was repelled by a crusading force.^[507]

The movement fostered the consolidation of western states by removing a substantial portion of their militant local elites and establishing precedents for concentrated taxation. Expanded commercial contact with the wider world encouragedurbanisation in western Europe. The sale of landed property weakened traditional structures founded on the personal ties between vassal and lord.^[508]

Crusading extended Western Christendom's frontiers in Iberia and the Baltic, promoting Catholic settlement and liturgical unity.^[509] Political expansion sometimes broughtlanguage change or evenextinction, as seen in the near-total disappearance of Arabic documents in Iberia by 1290 and the loss ofOld Prussian by 1680.^[510] Crusading also gave rise to national heroes and symbols, such as Denmark's flag, theDannebrog.^[511] Few existing institutions, mostly offshoots of former military orders, trace their origins to the crusading movement. The idea of Christian violence as an act of love persists in some interpretations, such asliberation theology.^[512]

Into the 20th century, France and Britain invoked the Crusades to justifyambitions in the Middle East.^[513] Today, they often symbolize a long-standing civilisational conflict.^[514] After9/11, PresidentGeorge W. Bush controversially called thewar on terror a "crusade".^[515] Muslim fundamentalists often label adversaries as "crusaders",^[516] and terms like "neo-Crusades" appear in popular discussions about Western or Russian military presence in the Middle East.^[517]Anti-Zionists frequently draw parallels between the Crusader states and modernIsrael.^[518]

Crusaders often donated relics to churches, and across Western Europe, statutes, frescoes, andstained glass commemorated the crusades.^{[note 55]} During theRomantic period, medieval crusading literature inspired artists, as seen in the 1830s decoration offive Versailles rooms with 120 paintings.^[520][521] Major works likeJerusalem Delivered byTorquato Tasso influenced later writers.^[522]Walter Scott'sIvanhoe (1819) andThe Talisman (1825) shaped popular depictions despite historical inaccuracies.^[523] To this day, Crusades-themedepic films exploit and reinterpret medieval imagery as both source and mirror of modern nations and conflicts.^{[note 56][527]} Depictions of the Crusades in modern cinema frequently draw historians' criticism; for instance, the argument of Riley-Smith that inKingdom of Heaven (2005), the directorRidley Scott conveyed a historical perspective akin toOsama bin Laden's.^[528]

Western Crusadehistoriography's first phase began with First Crusade accounts and continued untilc. 1600, amid ongoing Muslim–Christian conflict. Catholic historians interpreted the Crusades through anirredentist lens, framing them as efforts to reclaim Christian territory.^{[note 57][529]} The terminology was fluid, reflecting the movement's association with pilgrimage through terms such asiter ("journey"), while broader expressions, particularlyexpeditio crucis ("expedition of the cross"), were also employed.^[530]

A second phase began in 1611 with the publication of primary sources byJacques Bongars, later used byThomas Fuller, who completed a general Crusade history in 1639. Scholarship reflected strong ideological leanings: Protestants like Fuller were critical, whereas Catholics such asLouis Maimbourg were more sympathetic. Over time, terminology shifted—by the 18th century, neutral terms likeKreuzzug,croisade, and crusade replaced earlier expressions like "holy war".^[531]Enlightenment thinkers grew increasingly critical, exemplified byVoltaire's reference to the "madness of the crusades" (1751).^[520][532]

The third phase, beginningc. 1800, was shaped by nationalism and Romanticism, prompting a more positive reassessment. Landmark works includedFriedrich Wilken'sHistory of the Crusades from Eastern and Western Sources andJoseph-François Michaud'sHistory of the Crusades. In the 1830s,Leopold von Ranke introduced modernsource criticism, later applied byHeinrich von Sybel to the First Crusade. International collaboration advanced with the 1875 founding of theSociété de l'Orient Latin ("Society of the Latin East"). Critical editions of source material supported influential histories byRené Grousset (1930s) andSteven Runciman (1950s). Major later surveys include theWisconsin Collaborative History of the Crusades (1955–1989) and theOxford Illustrated History of the Crusades (1995).^[533] Early-21st-century scholarly debates focus on defining the Crusades, assessing participants' motives, and interpreting the movement through colonial or integrative models,^[534] and earlierEurocentric narratives are increasingly being challenged.^[535]

Muslim historiography largely overlooked the topic until 1899, when the EgyptianSayyid ʿAli al-Ḥarīrī wrote the first Arabic account.^[513][536] In the 2020s, theal-hurub al-salibyya ("wars of the cross") are central to education in Egypt and Jordan.^[537][517] The Syrian historian Soheil Zakkar compiled an encyclopaedia framing the anti-Frankish campaigns as a struggle for Arab liberation.^[538]

Greek historians have mainly studied thestavrósforía ("bearing of the cross") within Byzantine history,^[539] but Greek Cypriot scholars emphasize that the Third Crusade severed Cyprus from Byzantium and introduced a repressive regime.^[540] In Israel,Joshua Prawer's work established Crusade studies as a distinct academic field.^[518]

• History of Christianity
• Religious violence
• Christianity and violence