Poles
Polish people are the sixth largest national group in the European Union. Estimates vary depending on source, though available data suggest a total number of around 60 million people worldwide (with roughly 21 million living outside of Poland, many of whom are not of Polish ethnicity, but Polish nationals). There are almost 38 million Poles in Poland alone. There are also Polish minorities in the surrounding countries including (Germany), and indigenous minorities in the Czech Republic, Hungary, Slovakia, northern and eastern Lithuania, western Ukraine, and western Belarus. There are some smaller indigenous minorities in nearby countries such as Moldova. There is also a Polish minority in Russia which includes indigenous Poles as well as those forcibly deported during and after World War II; the total number of Poles in what was the former Soviet Union is estimated at up to 3 million.
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."