The Bloody Crusades
In May, 1096, in a period of four weeks frenzied bands of Crusaders struck the Jewish communities of Speyer, Worms, Mainz, and Cologne. The Jews were offered the option of conversion to Christianity or death; the vast majority chose the path of Kiddush HaShem, sanctification of G‑d's name. Rather than submit to forced conversion, in many cases Jews killed their wives and children, and then themselves. In the words of one of the Kinnos (lamentations) recited on Tisha B'Av: "Who can see it and not cry/As the child is slaughtered, the father recites the Shema/ Has such been seen or heard before?" Estimates of the toll taken on the Jewish communities range from 3,000 to 10,000 deaths.
These heroic martyrs have been immortalized in Jewish history as saintly people who reached the highest spiritual levels. In the Selichos service for the eve of Rosh HaShanah, Jews implore G‑d to remember those who sacrificed their lives: "The bloods of fathers and sons touched, the bloods of merciful women and their children touched, the bloods of brothers and sisters mixed, the bloods of grooms and brides, wise men and wise women, pious men and pious women, elderly men and women, young men and women, all mingled. O land, do not conceal their blood!"
Undaunted, unstoppable, the Crusaders conquered Eretz Israel, reaching Jerusalem in 1099. Once there, they gathered all the Jews of Jerusalem into the central synagogue and set it afire. Other Jews, who had climbed to the roof of Al-Aksa mosque on the Temple Mount, were caught and beheaded. The Crusader leader, Godfrey of Bouillon, wrote to the Pope, “If you want to know what has been done with the enemy found in Jerusalem...our people had their vile blood up to the knees of their horses.” After this victory, the Crusaders retained control of Jerusalem for close to 100 years.
https://www.chabad.org/library/article_cdo/aid/2617029/jewish/The-Bloody-Crusades.htm
