Antisemitism, an ancient prejudice that has lingered into the 21st century, has roots in an age when religion was felt to be central to one’s identity, morality, and place in society. During this time, the very existence of a rival religious group was seen almost as a provocation, and in Christian Europe the most visible example of this was Jewish people.

After the destruction of Jerusalem by the Romans in 70 CE and again in 135 CE, Jewish refugees immigrated widely throughout the Roman world, and by the Christian era were by far the largest non-Christian group in Europe. In the Middle Ages, their religious and cultural differences drew the suspicion and hostility of many Christians, who forced them to live apart in their own societies, which made them all the more mysterious to their Christian neighbors, some of whom spread fantastical rumors about their supposed practices. The most notorious of these was the macabre “blood libel”: the false claim that Jews ritualistically murdered Christian boys in order to use their blood in religious rites. As a result of these lies and other facile claims and grievances, Jews were a frequent target of pogroms—organized massacres, often by common citizens—and sometimes were expelled en masse from European countries.