The first Jewish population in the region to be later known as Germany came with the Romans to the city now known as Cologne. A "Golden Age" in the first millennium saw the emergence of the Ashkenazi Jews, while the persecution and expulsion that followed the Crusades led to the creation of Yiddish and an overall shift eastwards. A change of status in the late Renaissance Era, combined with the Jewish Enlightenment, the Haskalah, meant that by the 1920s Germany had one of the most integrated Jewish populations in Europe, contributing prominently to German culture and society. During The Holocaust many Jews fled Germany to other countries for refuge, and the majority of the remaining population were killed.