Territorial changes of Poland after World War II

The territorial changes of Poland immediately after World War II were very extensive. In 1945, after the defeat of Nazi Germany, Poland's borders were redrawn in accordance with the decisions made first by the Allies at the Tehran Conference of 1943 where the Soviet Union demanded the recognition of the military outcome of the top secret Nazi-Soviet Pact of 1939 of which the West was unaware.

The same Soviet stance was repeated by Josef Stalin again at the Yalta Conference with Roosevelt and Churchill in February 1945, but a lot more forcefully in the face of the looming German defeat. The new borders were ratified at the Potsdam Conference of August 1945 exactly as proposed by Stalin who already controlled the whole of East-central Europe.Harry Truman remembered:

I remember at Potsdam, we got to discussing a matter in eastern Poland, and it was remarked by the Prime Minister of Great Britain that the Pope would not be happy over the arrangement of that Catholic end of Poland. And the Generalissimo, the Prime Minister of Russia leaned on the table, and he pulled his mustache like that, and looked over to Mr. Churchill and said: Mr. Churchill, Mr. Prime Minister, how many divisions did you say the Pope had?”

The prewar eastern Polish territories of Kresy, which the Red Army had overrun during the Nazi-Soviet invasion of Poland in 1939 (excluding the Białystok region) were permanently annexed by the USSR, and most of their Polish inhabitants expelled. As a result of the Potsdam agreement to which Poland's government-in-exile was not invited, Poland lost 179,000 km2 (45%) of prewar territories in the east, including over 12 million citizens of whom 4,3 million were ethnically the speakers of Polish. Today, these territories are part of sovereign Belarus, Ukraine, and Lithuania.

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