Except for the Mongols, the crusaders confronted familiar enemies, portrayed as aggressors and thus furnishing a just cause for war. Conquest and colonisation produced multi-ethnic societies. In Iberia and the Crusader states, relations with native populations broadly followed the pre-conquest model, relegating non-Catholic ethno-religious groups to second-class status.
Muslims of the
Quran, placed in
the madrasa of
Nur al-Din in Damascus Muslim legal experts
divided the world into (the
Muslim world) and (non-Muslim lands). Border regions like Syria and Iberia became battlegrounds, attracting
military volunteers— and —from across . 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. Sporadic attacks on pilgrims likely shaped perceptions of danger, though Asbridge highlights that interfaith violence mirrored broader political and social turmoil. Western Christians often mislabelled Muslims as idol-worshippers or heretics. Until , massacres of Muslims in conquered towns were common. Violence was presented as a response to the Muslim occupation of the holy places and the oppression of Christians. Later, crusaders rarely sought conversions, instead levying a poll tax akin to the . Church law imposed restrictions on Muslims, though enforcement is poorly documented. In the Crusader states, most Muslims—Arabic-speaking farmers—lived in self-governed communities under
Islamic law. In Iberia, —Muslims under Christian rule—also faced second-class status. Initially, few Muslims perceived the Crusades' religious character, and longstanding conflicts among Muslim rulers persisted. The Damascene scholar
al-Sulami was the first to situate them within broader "
Frankish", or Westerner, expansion. He interpreted their success as divine punishment for neglecting . Zengi was among the era's first Muslim leaders receiving honours. Later rulers likewise invoked religious motives in anti-Frankish campaigns. In Iberia, the
Almoravids and the
Almohads strongly supported . Nonetheless, pragmatic Christian–Muslim alliances remained common throughout the period.
Eastern Christians near Bethlehem. Its restoration was financed by the Byzantine emperor
Manuel I Komnenus during the Crusading period. The liberation of eastern Christians was proclaimed a central aim of the First Crusade, yet early encounters proved disappointing. 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. Soon after Antioch's capture, Crusader leaders described local Christians as "heretics" in a letter to Pope Urban. In the Crusader states, Eastern Christians paid a poll tax, signalling their subordinate status, although their self-governance was reinforced and some retained considerable landholdings. Orthodox Christians, or
Melkites, formed the majority of Palestine's native Christian population and were also prominent in northern Syria. Catholic theologians regarded them as
schismatics rather than heretics. Although most Orthodox bishops had fled Palestine before 1099, scattered references suggest the presence of an Orthodox hierarchy under Frankish rule. Monasticism experienced a revival under Byzantine patronage. Certain Eastern Christian communities were treated as heretics for rejecting the
Council of Chalcedon, whose teaching on Christ's two
natures (divine and human) was central to both Catholic and Orthodox theology. Among them, the
Armenians—concentrated in northern Syria and
Cilicia—maintained autonomous lordships. Many welcomed the crusaders, and Armenian aristocrats formed marriage alliances with them. This cooperation led to a tenuous
church union with Rome (1198) and ultimately to the Frankish
Lusignans' rule over
Cilician Armenia.
Syriac (or Jacobite) Christians, mainly rural and Arabic-speaking, were viewed with suspicion and condescension; yet the Jacobite patriarch
Michael the Syrian praised Frankish religious tolerance contrasting it with Byzantine policy. Another distinct group, the
Maronites of
Mount Lebanon, entered into communion with Rome, forming the first
Eastern Rite Catholic Church in 1181. Byzantine–Frankish relations were variable. Following the Fourth Crusade, Byzantine successor states like
Epirus and
Nicaea led resistance against the conquerors, although temporary Greek–Frankish alliances were not uncommon. In
Frankish Greece, many Greek (aristocrats) retained lands and fought alongside Franks. Peasants suffered harsher conditions than under Byzantine rule. Orthodox bishops refusing papal supremacy were replaced by Catholic appointees, but Greek monasteries received papal protection. Latin conquest reinforced Orthodox identity, and persistent local resistance ultimately thwarted attempts to church reunification. 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 and
Rus' leaders, lasting control over Rus' lands was never achieved.
Pagans 's
papal bull about the baptism and coronation of the Lithuanian ruler
Mindaugas Trade in raw materials and
slaves had long connected Christian and pagan communities in the
Baltic region, although rivalry over trade routes often sparked armed conflict. From , intensified
German colonisation and unequal access to resources triggered more frequent clashes between the Wends and their Christian neighbours. In 1146, while promoting the Second Crusade, the Cistercian abbot
Bernard of Clairvaux encountered Saxon reluctance to abandon anti-Wendish campaigns. Adopting their perspective, he convinced to proclaim the Wendish Crusade. The Wends' structured society—with principalities, towns, and a priestly hierarchy—eased their eventual integration into Christendom. Further east, the
Old Prussians,
Latvians, and
Curonians had long resisted
Christianisation. They lived in rural communities led by strongmen who thrived on trade and raiding. Crusaders employed coercion, bribery, and promises of protection to gain converts among them.
Papal legates sought to protect the converts from exploitation but achieved little. The
Lithuanians, largely taxpaying peasants under
native lords, unified in the 13thcentury under Grand Prince
Mindaugas. Baptized in 1253, he received a royal crown from
Pope Innocent IV but later reverted to paganism. In 1386, Grand Prince
Jogaila married Queen
Jadwiga of Poland. The subsequent
mass conversion of Lithuanians to Catholicism eroded the Teutonic Knights' justification for crusade. In 1410, Polish-Lithuanian forces decisively defeated the Knights in the
Battle of Grunwald. The waned, and the last non-German crusaders entered the Baltic in 1413. In the eastern Baltic, Finnic peoples lived in small rural communities, sustained by farming, slave-raiding, and fur-hunting. Legend has it that
Eric IX of Sweden led a
crusade to Finland in the 1150s, but the earliest confirmed expedition was authorized by
Pope Gregory IX in 1237. Danish crusaders conquered
Estonia in 1219, but by mid-century, German knights and
burghers dominated the region's politics.
Western dissidents at the beginning of the
Albigensian Crusades (a miniature from the late 14th-century ). The Gregorian Reform did not satisfy those seeking a purer, simpler Christianity.
Increased trade carried
dualist ideologies westward, distinguishing between an incorruptible God and an evil
creator of the material world. In Western Europe, their adherents became known as
Cathars or Albigensians. As Catholic churchmen saw heresy as a fundamental threat to the faith and to salvation, the
Third Lateran Council granted indulgences, in 1179, to those who fought heretics. Yet, in southern France, Cathars were deeply embedded in
Occitan society, and local elites were unwilling to act against heretical friends or kin. In 1207, Pope InnocentIII urged
Raymond VI, Count of Toulouse, to eradicate heresy. His reluctance or inability to comply led to excommunication by the papal legate
Peter of Castelnau, who was soon murdered. In response, Innocent declared the first
Albigensian Crusade. Northern French crusaders invaded Occitania, committing atrocities against both Cathars and Catholics. Though the campaigns strengthened French influence, they failed to eliminate heresy. That was eventually achieved by
mendicant friars,
inquisitors and secular authorities. The
Stedinger Crusade in northern Germany targeted peasants accused of heresy for refusing to pay the
tithe (church tax). Hungarian rulers led
two failed crusades into
Bosnia, allegedly home to a Cathar
antipope. The radical in northern Italy were swiftly crushed by crusading forces.
Mongols after the
Battle of Legnica (from a mid-15th-century
Legend of his mother
St Hedwig) In 1206, Temüjin was proclaimed
Genghis Khan, uniting the Mongol tribes under the belief in a
divine destiny to conquer the world. Western Europeans first learned of the
earliest Mongol conquests during the Fifth Crusade. As some tribes followed the
Eastern Syriac (Nestorian) Church, the Mongols came to be linked in Western thought to the people of the mythical Christian ruler
Prester John, prompting hopes of an anti-Muslim alliance. The
Mongol invasion of Eastern and Central Europe in 1239–42 shocked Western Christendom. Although Pope GregoryIX called for a crusade, the Mongols withdrew from Europe following the death of
Ögedei Khan, Genghis's successor, in 1242. In the Middle East, Mongol forces
sacked Baghdad and destroyed the Abbasid Caliphate in 1258. Seeking protection,
Hethum I of Cilician Armenia and
Bohemond VI of Antioch submitted to
Hulegu, the Mongol (ruler of the Middle East). The
Ilkhanate's expansion ended in 1260 when Mamluk forces defeated Hulegu's army in the
Battle of Ain Jalut.
Jews Late Roman legislation and Christian theology shaped Western attitudes to
Judaism. It remained legally recognised, yet its adherents faced restrictions and were seen as divinely preserved but punished with
dispersion for rejecting Jesus. Jewish migration to Western Europe coincided with the pre-Crusade economic boom. Coming from developed Islamic economies, Jewish merchants brought advanced commercial expertise. Free from canon law's anti-
usury rules, they came to dominate moneylending, fuelling
antisemitism. Local rulers valued Jewish economic contributions and offered protection, though often fragile. Organized pogroms began
in the Rhineland during the First Crusade, reportedly driven by vengeance
for Christ's death and desire for Jewish property. In Jerusalem, crusaders massacred Jews, though communities in other towns—such as
Tyre and
Ascalon—survived.
Jewish pilgrimage to the Holy Land intensified; hundreds of
western Jews settled there during the Crusades era. Although
Pope Calixtus II's bull forbade violence against Jews, crusade preaching repeatedly incited antisemitic pogroms. ==Women==