As a result of the Soviet invasion of Poland in 1939 , hundreds of thousands of Polish soldiers became prisoners of war in the Soviet Union . Thousands of them were executed ; over 20,000 Polish military personnel and civilians perished in the Katyn massacre . Out of Anders ' 80,000 evacuees from Soviet Union gathered in the United Kingdom only 310 volunteered to return to Poland in 1947
Katyn massacre
Katyn massacre
Prisoner of war