World War II created the greatest refugee problem in human history. The problem began before the actual fighting broke out. And by the end of the war, millions were dead and the survivors on the move all over Europe trying to return home, although for many this was not possible. The problem was concentrated in Europe, but not entirely confined there.

The problem began with the Nazi take over in Germany (1933). Political opponents fled Germany as did many Jews. The Nazi regime's focus on biological racism was to play a major role in the World War II refugee problem. Refugees from the fighting were a small part of the overall refugee problem. The Nazis were determined to remake not only the political map of Europe, but also the ethnic map. And to do this they decided not only to create a colonial empire, but to use genocide.

There were forced deportation, mass evacuation and displacement, persecution based on ethnicity, mass killing, and conscription for forced labor, anti-partisan operations, intra-ethnic violence, strategic bombing and evacuation from the cities. The Nazi approach to many refugee groups shifted toward genocide as the war progressed. There were refugee problems in most of the countries involved in World War II. And the border changes at the end of the war caused additional refugees.

The refugee crisis in Europe, especially Germany, resulted after the War in the creation of an international refugee and human rights infrastructure which is the basis of how refugee problems are handled today.