The correct answer to this open question is the following.
The Black Death was the common name for the Bubonic Plague that killed millions of people in Europe and Asia in the Middle Ages. The plage also affected Jewish people but not as hard as other ethnicities because Jewish people had different and more strict hygienic habits. Historians consider that 20 percent of the Jewish perished due to the Black Death.
The crusades also affected Jews, For instance, the Crusades captured Jerusalem in 1099, killed all Muslims there and forced Jews to surrender in Palestina to the Crusaders, otherwise, they would have died. Jews in the Rhineland also were forced to surrender to the new rule.
