To treat the demography of the Jewish population of Eastern Europe—its size, its movement within the region, and migration from it—this entry includes three articles. The principal division is chronological, using World War I, a time of great upheaval that disrupted large numbers of people and an event that led to the end of the empires of Eastern Europe and a redrawing of the area’s political map, as the point of division. The first article covers population and migration before World War I; the second and third articles separately treat these topics after the war. For further discussion, see the entries on specific countries, regions, and cities.