Hungary) under the Potsdam Agreement from 1945 to 1948 towards the end and after the war. Both those who became ethnic Germans by registering in the Deutsche Volksliste and Reichsdeutsche retained German citizenship during the years of Allied military occupation, after the establishment of East Germany and West Germany in 1949, and later in the reunified Germany. In 1953 the Federal Republic of Germany - by its Federal Expellee Law - naturalised many more East European nationals of German ethnicity, who neither were German citizens nor had enrolled in any 'Volksliste', but had been stranded as refugees in West Germany and fled or were expelled due to their German or alleged German ethnicity. An estimated 12 million people fled or were expelled from the Soviet Union and non-German-speaking Central Europe, many of them being 'Volksdeutsche'.The Expulsion of 'German' Communities from Central and Eastern Europe at the end of the Second World War, Steffen Prauser and Arfon Rees, European University Institute, Florense. HEC No. 2004/1. p.4 Most left the Soviet-occupied territories of Central and Eastern Europe; they comprised the largest migration of any European people in modern history.Bernard Wasserstein, Barbarism and civilization: a history of Europe in our time, Oxford University Press, 2007, p.419: "largest population movement between European countries in the twentieth century and one of the largest of all time." The then three Allies had agreed to the expulsions during negotiations in the midst of war. The western powers hoped to avoid ethnic Germans being an issue again in Central and Eastern Europe.Detlef Brandes, Der Weg zur Vertreibung 1938-1945: Pläne und Entscheidungen zum "Transfer" der Deutschen aus der Tschechoslowakei und aus Polen, Munich: Oldenbourg Wissenschaftsverlag, 2005, pp. 398ff, The three Allies at the Conference of Potsdam considered the "transfer" of "German populations" from Czechoslovakia, Poland and Hungary an effort to be undertaken (see article 12 of the Potsdam Agreement), although they asked a halt because of the inflicted burden for the Allies to feed and house the destitute expellees and to share that burden among the Allies. France, which was not represented in Potsdam, rejected the decision of the Three of Potsdam and did not absorb expellees in its zone of occupation. The three Allies had to accept the reality on the ground, since expulsions of Volksdeutsche and Central and Eastern European nationals of German or alleged German ethnicity who never had enrolled as Volksdeutsche, were going on already.