Germany had started the Second World War in an intentional and conscious manner, obviously being aware that every action can have unpredictable and unwanted consequences. The Potsdam decisions were taken by the Great Powers after assuming supreme authority in Germany. They constituted a manifestation of the Allies’ rights and responsibilities. The territorial changes of Germany and the transfer of population were part of the general regulation of the effects of the Second World War. These decisions were not a simple matter of revenge. They must be perceived in a wider political perspective of European policy. The resettlement by Germany of ethnic Germans to the Reich or to the territories it occupied constituted an instrument of National Socialist policy. This German policy turned out in 1945 to be a tragic irony of fate. The resettlement decided in Potsdam must be perceived in the context of German legal responsibility for the war’s outbreak. The individual perception of the resettlement and individual guilt are different from the international responsibility of the state and from the political-historical responsibility of the nation. In our discussion we made the distinction between the individual and the collective aspect as well as between the legal and historical/political aspect. We deal with the guilt of individuals (criminal, political, moral), the international legal responsibility of states, and the political and historical responsibility of nations (societies). For the difficult process of understanding and reconciliation between Poles and Germans, the initiatives undertaken by some social circles, and especially the church, were of vital importance. The question of the resettlement became a theme of numerous publications in Poland after 1989. In the mid 1990s there was a vast debate in the media with the main question of: should we apologize for the resettlement? Tracing a line from wrongdoing/harm to unlawfulness is not easy. In 1945 the forcible transfer of the German population was an act that was not prohibited by international law. What is significant is that this transfer was not a means of war conduct. It did not apply to the time of a belligerent occupation, in terms of humanitarian law, but to a temporary, specific, international post-conflict administration. Maybe for some people Potsdam decisions will always be seen as an illegal action, for others as an expression of strict international legal responsibility, for some as a kind of imperfect justice, and still for others as an opening of a new opportunity for Europe.