Ashkenazi migrations throughout the High and Late Middle Ages
Historical records show evidence of Jewish communities north of the Alps and Pyrenees as early as the 8th and 9th century. By the early 900s, Jewish populations were well-established in Northern Europe, and later followed the Norman Conquest into England in 1066, also settling in the Rhineland. With the onset of the Crusades, and the expulsions from England (1290), France (1394), and parts of Germany (1400s), Jewish migration pushed eastward into Poland, Lithuania, and Russia. Over this period of several hundred years, some have suggested, Jewish economic activity was focused on trade, business management, and financial services, due to Christian European prohibitions restricting certain activities by Jews, and preventing certain financial activities (such as "usurious" loans) between Christians.
The Polish-Lithuanian Commonwealth at its greatest extent.
By the 1400s, the Ashkenazi Jewish communities in Poland were the largest Jewish communities of the Diaspora. Poland in this time was a decentralized medieval monarchy, incorporating lands from Latvia to Romania, including much of modern Lithuania and Ukraine. This area, which eventually fell under the domination of Russia, Austria, and Prussia (Germany), would remain the main center of Ashkenazi Jewry until the Holocaust.