Later, during World War II, the Soviets occupied vast areas of eastern Poland (so called Kresy), another 5.2-6.5 million of Poles (from the total population of about 13,5 million of these territories) were added. Some claim that as many as 1.7 million of Poles were later deported to far away territories of USSR, such as Siberia. Other historians gave a much lower estimation, about half a million of Poles murdered and deported.
After World War II most of Poles from Kresy were expelled into Poland, but officially stated 1.3 mil stayed in USSR. Some of them stayed motivated by traditional Polish belief, that one day they can become again lawful owners of the land they live on. Some of the them were kept forcefully in. There are reasons to believe that those expelled were more happy that those, who stayed.
Polish minority was one of the few whose numbers decreased over time, according to offical statistics. They also belonged to the least educated ethnic group, which allegedly was caused by ethnic persecutions.
After 1989 started emigration of Poles who survived in Kasakhstan, mainly to Russia and, supported by society immigration to Poland. The number remaining is put between 50 000 and 100 000.
After 1991 Poles became minorities in: Lithuania around 250 000 (7% of population), Belarus at least 420 000, Ukraine at least 150 000 and Russia more then 100 000.