The German Crusade of 1096 was the part of the First Crusade in which peasant crusaders from France and Germany attacked Jewish communities. Although anti-Semitism had existed in Europe for centuries, this is the first record of an organized mass pogrom.
Pope Urban II did not mention the Jewish people when preaching the First Crusade, and later condemned any violence perpetrated against the Jews. In some cases, authorities and religious leaders attempted to shelter their Jewish subjects.

Background
In the spring of 1096, a number of small bands of knights and peasants, inspired by the preaching of the Crusade, set off from various parts of France and Germany. The crusade of the priest Folkmar, beginning in Saxony, persecuted Jews in Magdeburg and later, on May 30, 1096 in Prague in Bohemia. The Catholic Bishop Cosmas attempted to prevent forced conversions, and the entire Catholic hierarchy in Bohemia preached against such acts.

Emicho
Later in 1096, Godfrey of Bouillon also collected tribute from the Jews in Mainz and Cologne, but there was no slaughter in this case. After the success of the First Crusade in the Holy Land, the Jews in Jerusalem were either slaughtered along with the Muslims, or expelled and forbidden from living in the city, unlike the traditional Islamic tolerance -at the price of a tax- for Christians and Jews.
The First Crusade ignited a long tradition of organized violence against Jews in European culture. Jewish money was also used in France for financing the Second Crusade; the Jews were also attacked in many instances, but not on the scale of the attacks of 1096. In England, the Third Crusade was the pretext for the expulsion of the Jews and the confiscation of their money. The two Shepherds' Crusades, in 1251 and 1320, also saw attacks on Jews in France; the second in 1320 also attacked and killed Jews in Aragon (Spain).

Jewish reactions

Albert of Aix, Historia Hierosolymitana
Robert Chazan, European Jewry and the First Crusade. University of California Press, 1987.
Robert Chazan, In the Year 1096: The First Crusade and the Jews. Jewish Publication Society, 1996 (also contains extracts from the Hebrew chronicles).
Jeremy Cohen, Sanctifying The Name of God: Jewish Martyrs and Jewish Memories of the First Crusade. University of Pennsylvania Press, 2004.
Kenneth Setton, ed., A History of the Crusades. Madison, 1969-1989 (available online).
see also First Crusade Selected Sources