These decisions were 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 line proposed by British Foreign Secretary Lord Curzon in 1920.[3]
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?[5]
The population transfer of both Polish and Germans 1945–46 included many millions of people.[7][8] The Polish territory in 1919–39 covered an area of 386,418 square kilometres (149,197 square miles).[9] But from 1947, Poland's territory was reduced to 312,679 square kilometres (120,726 square miles), so the country lost 73,739 square kilometres (28,471 square miles) of land. This difference amounts almost to the size of the Czech Republic, although Poland ended up with a much longer coastline on the Baltic Sea compared to its 1939 borders. In addition, the infrastructure in the former eastern territories of Germany was more developed than in the territories ceded to the Soviet Union.[citation needed]
The German population who had stayed at or had returned to their homes were forcibly expelled before these Recovered Territories (official term) were repopulated with Poles from Central Poland and by Poles expelled from the eastern regions and those from central Poland. The borders of Poland resembled the borders of the German-Russian gains in World War 2, with the exception of the city of Bialystok. This is called the Curzon line. The small area of Trans-Olza, which had been annexed by Poland in late 1938, was returned to Czechoslovakia on Stalin's orders.