Launched by Pope Urban II in 1095 and encompassing greater Christian Europe, to retake ‘Christian lands,’ including ultimately Jerusalem, from the Muslim conquest.
Severe massacres of (civilian) Jews during the First Crusade.
Rosemary Ruether writes:
“The pogroms of the Crusades were met with stoic heroism by the Jewish communities of the Rhineland. Refusing the baptism offered at sword’s point by the Crusaders, they regularly submitted to death or committed mass suicide rather than be baptized. A martyr ethic was forged in European Jewry. The Christian doctrine of the Trinity was regarded as polytheism and its view of Jesus’ divinity as idolatry. To resist baptism was comparable to the witness of the ancient martyrs of Israel, who resisted to the death the assaults of paganism at the time of the Maccabees. Jews died uttering the Shema’ as witnesses to the unity of God’s Holy Name.*A This resistance of the Jews to baptism was inexplicable to Christians.” (Ruether, Faith and Fratricide, p. 207).
*A For medieval Jewish martyr theology, see especially Jacob Katz, Exclusiveness and Tolerance (New York: Schocken, 1969; reprint), pp. 82–92.