 Complete the following phrase:  The population of Poland decreased by about six million due to the losses sustained during the Holocaust and German occupation during World War II 1939-1945, and Poland became one of the most ethnically homogeneous areas in Europe next to the populations of Slovakia and the Czech Republic as a result of radically altered borders and population expulsions at the end of and after the war. The post-war population movements were accompanied by waves of forced migrations ordered by the Soviet and Polish communist authorities, including the 