Christian anti-Semitism was strongly present before the Crusades. The existence of large Jewish communities throughout Europe and the Middle East was quite strong. However, their presence was rather tolerated than accepted. The Christian views on Jews were unfriendly because the Jews had the money lending business to themselves, while depriving Christians from lending. When the Crusades started the Jews served as a tempting target trapped between two rivalry religions: the Christians and the Muslims.
The Muslim presence in the Holy Land had been established since the 7th century when the Muslims conquered Palestine putting increasing pressure on the Eastern Orthodox Byzantine Empire. The main goal of the Christian Western Europe with the Crusades was to recapture Jerusalem from the Muslims and to impede the expansion of Seljuk Turks into Anatolia.
The poor relations between the Christians and the Muslims only deteriorated. By 1096, a huge army of Crusaders between 25,000 to 30,000 men was ready to fight upon the call of Pope Urban II. Marching Southern France to Constantinople, they faced the resistance of the Byzantines, who were not prepared for such friction. In 1097, they left Constantinople for going to Jerusalem. On July 15, 1099, Jerusalem was captured by Godfrey of Bouillon, leader of the First Crusade, who invaded it through the Jewish quarter. The order of Caliph Al-Hakim to demolish the Church of Holy Sepulchre and all Christian buildings in Jerusalem fired new frictions.
Jews, greatly displeased with the behavior of Christians towards them all the previous years, chose to fight side-by-side with the Muslims to defend Jerusalem against the Crusaders. To escape death, they were seeking refuge in the synagogues, while their Muslim neighbors were hiding in the mosques. The First Crusade resulted in the extreme massacre of Muslims in the al-Aqsa Mosque and the burning of Jews in the main synagogue. Jewish survivors were sold as slaves and they were later redeemed by Jewish communities in Italy. According to many historians, this was the end of the Jewish community in Jerusalem.
Since 1096, the intellectual and social activity of the Jewish community in Jerusalem was discontinued. Moreover, the Crusades had created two other groups that harmed the Jews: itinerant preachers, who were mostly interested in taking financial advantage of the Jews, and the German peasants, who exercised immense violence upon the Jews. When the Crusades began, the German peasants destroyed many Jewish communities in Mainz and Worms by slaughtering people, flaming synagogues and massacring innocent people.
The number of Jewish victims during the First Crusade in Europe is hard to measure. Jewish historians, but also their European peers, estimate that is more than 10,000 people, which makes up to three quarters of the Jewish population of that time. In majority, they were killed outright, while some were offered the option of baptism and conversion to Christianity.
The reasons for the extreme persecution of Jews during the Crusades are a highly controversial issue. Historical archives suggest that the explicit cause of the Crusades was the continuous reporting from Jerusalem regarding the abuse of Christian pilgrims and their prohibited access to the Holy Places by the Muslims. However, in these reports, the malevolent involvement of the Jews was also mentioned. Historians believe that this served to the preparation of the ground for the inclusion of the Jews in the animosity against anyone non-Catholic.
In addition, Christians hated Jews for the crucifixion of Jesus and accused them for performing anti-Christian rituals where the sacrifice of Christian children was a common pattern. According to Jewish historians, the Jews were often the scapegoats for anything that was going wrong in the community. Forced to live in ghettos, Jews were treated by Christians like second-class citizens. In contrast, according to European historians, Jews were practicing these rituals as a part of their religion. However, both sides agree that in such turbulent times, it is difficult to derive safe conclusions. In the Middle Ages, Christianity was the prevalent religion in Europe. However, there was a clear ambition to make it a prevalent religion in the world eliminating or confining any outsiders like the Jews, but also Muslims, Orthodox Christians, Mongols, Slavs and anyone non-believer in the Catholic Church.
After the First Crusade, a wave of emotional, religious Christian rage exploded. Reflected in the slaughter of Jews by Crusader mobs throughout Europe, but also in the aggressive treatment of “schismatic” Eastern Orthodox Christians, the Crusades became an emblem of Christian wrath. There were some great examples of Christian Bishops and plain Christian people, who tried to offer asylum to Jews to protect them from the mobs. Also, Jews were offered shelter in Christian churches and other Christian buildings.
During the Second Crusade (1145-1147) Jews were not disturbed or destroyed, but their doctrine was put forward to witness the correctness of Christianity. Becoming living symbols of the Passion, Jews were not murdered, but they were punished by dispersion to be saved by definitive conversion to Christianity.
The Third Crusade (1189–1192) was mainly characterized by Jewish pogroms in England.
The Crusades shaped the turning-point in the medieval history of the Jews. Their massacre during the Crusades destabilized fatally their economic and social position. Christian anti-Semitism became even stronger than before making the Jews less important. Having lost control on trade and money, the Jews have become extremely vulnerable.
Many historians believe that there are many common elements between the Crusades and the Holocaust. The first well-documented pogroms against the Jews occurred during the Crusades. Although violence was prohibited by the various Popes, the Crusaders did not protect the Eastern Christians and neither did protect the Jews. Instead, they destroyed their communities, burned their houses, and massacred the people making Jerusalem a dreadful pogrom, in which all the Jews who were not expelled were massively executed.