Demographics of Poland
According to GUS, about 38,325,000 people live in Poland, however, the same report states that the number of residents living in the country all the time is approximately 37,200,000; with 1,125,000 people living abroad for 6 to 7 months or more. It means that the permanent population may be correspondingly smaller.
Soviet partisans
After the German invasion of Poland in 1939, which marked the beginning of World War II, the Soviet Union invaded the eastern regions of the Second Polish Republic (referred to as the "Kresy") and annexed the lands totalling with a population of 13,299,000 inhabitants including ethnic Belarusians, Ukrainians, Poles, Jews, Czechs and others. Belarusian emigre sources said that the actual number of Belarusians in Poland in 1931 was over 3.4 million or 77.9 percent of the total population in West Belarus. A Ukrainian geographer concluded that out of 9,198,000 people living in western Ukraine (Galicia and Volhynia), Ukrainians amounted to 64.5 percent. Soviet era sources state that in 1939, Soviet forces took control of regions of the Polish Republic that had "a population of more than 12 million, including more than 6 million Ukrainians and about 3 million Belarusians."