Well, there were a number of Jews who fled to Germany in the late 19th, early 20th centuries due to oppression in a number of eastern european countries. Germany was willing to take them in, as it treated Jews in a more liberal manner at that time. Jews fled to a number of other western European countries and the US as well, not just Germany. The oppression that spurred the exodus of Jews took the form of pogroms, which were basically anti-semitic attacks where Christian villagers attacked Jewish areas, killing, raping, burning, and stealing. They mostly took place in Russia, specifically in the area that is now Ukraine and Belarus.