The Crusades were a series of military campaigns launched by the papacy between 1095 and 1291 against Muslim rulers for the recovery and defence of the Holy Land, encouraged by promises of spiritual reward. The First Crusade was proclaimed by Pope Urban II at the Council of Clermont in November 1095, a call to arms for Christians to reconquer Jerusalem from the Muslims. By this time, the papacy's position as head of the Catholic Church had strengthened, and earlier conflicts with secular rulers and wars on Western Christendom's frontiers had prepared it for the direction of armed force in religious causes.The successes of the First Crusade led to the creation of four Crusader states in the Middle East, whose defence required further expeditions from Catholic Europe. The organisation of such large-scale campaigns demanded complex religious, social, and economic institutions, including crusade indulgences, military orders, and the taxation of clerical income. Over time, the crusading movement expanded to include campaigns against pagans, Christian dissidents, and other enemies of the papacy, promoted with similar spiritual rewards and continuing into the 18th century.
The Crusade of 1101, the earliest papally sanctioned expedition inspired by the First Crusade, ended in disastrous defeats. For several decades thereafter, only smaller expeditions reached the Holy Land, yet their role in consolidating and expanding the Crusader states was pivotal. The fall of Edessa, the capital of the first Crusader state, prompted the Second Crusade, which failed in 1148. Its failure reduced support for crusading across Latin Christendom, leaving the Crusader states unable to resist Saladin's expansion. Having united Egypt and Muslim Syria under his rule, Saladin destroyed their combined armies at the Battle of Hattin in 1187. The Crusader states survived largely owing to the Third Crusade, a major campaign against Saladin, though Jerusalem remained under Muslim control. Initially directed against Egypt, the Fourth Crusade was diverted to the Byzantine Empire, culminating in the Sack of Constantinople and the establishment of the Latin Empire in 1204. The Fifth Crusade again targeted Egypt but failed to conquer it in 1219–21. By this period, crusade indulgences could also be obtained through other campaigns—such as the Iberian, Albigensian, and Northern Crusades—thereby diminishing enthusiasm for expeditions in the eastern Mediterranean.
