Toward the end of the 11th century, tensions grew between Christians and Muslims, driving the two religious groups into a long and violent holy war, also known as the Crusades. Between 1095 and 1291, the Roman Catholic Church sent Crusaders to the Middle East to wage war against the Muslims in hopes of regaining control of Jerusalem, earning passage back into the Holy Land and hindering the spread of Islam.

Causes

Although Muslims controlled approximately two-thirds of the ancient Christian world in the Middle East by the 11th century, they and the Roman Catholic Church had a mutual understanding that those who wished to make the pilgrimage eastward would be allowed to do so freely and without persecution. For Christians, Jerusalem was particularly significant because the Church of the Holy Sepulchre commemorates the hill of crucifixion and tomb of Christ's burial. However, in 1065 the Seljuk Turks took control of the Holy Land and massacred 3,000 Christian pilgrims, infuriating the Church. In 1095, Pope Urban II pleaded with and persuaded the Council of Clermont in France to approve a holy war against the Muslims in order to avenge the deaths of the pilgrims and halt the Turks' expansion on the world stage.

The People's and the First Crusade

In 1095, the first of the Crusaders were scheduled to convene in Constantinople and then journey together toward the Holy Land. Before they were able to do so, however, thousands of men, women and children from the lower social classes assembled and journeyed toward Jerusalem in hopes of fighting the Turks themselves. This crusade, called the People's Crusade, ultimately failed as a result of lack of training and proficient leadership.

When the knights of the First Crusade made their voyage, they too experienced power struggles as well as violence on the road through the Middle East. By the time they reached Jerusalem, the Turks had been ousted by Egyptians, but this alteration did not deter the Christians from fighting for what they believed was their sacred city. After much fighting, the First Crusade was successful in winning over Muslim territory and momentarily establishing the Latin kingdom of Jerusalem.

The Second Through Fourth Crusades

Although the first four Crusades are the most recognized of the nine, as well as the most well-orchestrated by the Church, fighting between Christians and Muslims endured for a total of 200 years. The Second Crusade, participated in by the French king Louis VII and the Holy Roman Emperor Conrad III, resulted in military failure with the only advances made in Portugal, where Lisbon was liberated from the Moors. The Third Crusade, which took place between 1189 and 1192, is recognized for the Christian's effort to take back Jerusalem from Saladin, the Muslim founder of the Ayyubid dynasty. For the Christians, this effort was ultimately a failure. The Fourth Crusade also was meant to recapture Jerusalem, but failed when Constantinople (the capital of the Byzantine empire) was sacked and fell in 1204.

The Fifth Through Ninth Crusades

The Roman Catholic Church attempted to regain the Holy Land with the fifth through ninth Crusades, lasting into the 13th century. However, because they were not significantly large military endeavors, they were not close to being successful. Efforts continued to hinder Islamic expansion, but were organized by political figures who were motivated by personal causes. Organization and enthusiasm for participation declined, culminating In 1291, when the last of the Christian mainland strongholds at Acre (also called Akko) could not withstand Muslim onslaught with only a minimal force for defense. Despite the fact that there were still religious footholds in Cyprus and Rhodes, the Crusading effort was quashed.

Effects

Despite the fact that thousands were killed in the Christian effort to regain Jerusalem and the Holy Land, it is believed that there were positive effects resulting from the Crusades. The interactions between Eastern and Western cultures opened trade routes and depots and introduced Middle Eastern products such as textiles and foods, as well as higher levels of learning and medicine. Muslim culture at the time was more cosmopolitan than that of the Christians, which is believed to have spurred ingenuity and helped the West recover from the Dark Ages and enter the Renaissance period.