German-Polish relations

German–Polish relations have a long and complicated history.

From the 10th century on, the Piast Kingdom of Poland established under Duke Mieszko I had close and chequered relations with the Holy Roman Empire. However, these relations were overshadowed by the centuries-long Polish–Teutonic Wars, as a result of which the Teutonic Duchy of Prussia became a fief of the Kingdom of Poland. Prussia retained a certain level of autonomy under Polish rule. Later, the Kingdom of Prussia rose and eventually became one of the partitioners of Poland in 1772–1795.

In 1918, Poland regained its place on the map. After World War I, the Treaty of Versailles deprived Germany of its territories in West Prussia, East Upper Silesia and Danzig and transferred them to Poland. It was seen as a great injustice in the Weimar Republic, in part leading to the Nazi takeover of power in 1933. On 1 September 1939 Poland was invaded by Germany, thus starting World War II. The Third Reich established concentration camps in German occupied Poland, the biggest located in Auschwitz. Poland suffered many casualties and a vast destruction during the war. After World War II, Germany lost its former eastern territories to Poland and the Soviet Union. In 1945-1950, a series of expulsions happened, in which up to 16 million ethnic Germans were forced to leave their homes and resettle in post-war Germany. It was the largest forced movement of any population in history.