The Republic of Poland was a multicultural country before World War II , with almost a third of its population originating from the minority groups : 13.9 % Ukrainians ; 10 % Jews ; 3.1 % Belarusians ; 2.3 % Germans and 3.4 % percent Czechs , Lithuanians and Russians . Members of the German minority resided predominantly in the lands of the former German Empire but not only . Many were hostile towards the existence of the Polish state after losing their colonial privileges at the end of World War I. German organizations in Poland such as '' Deutscher Volksverband '' and the '' Jungdeutsche Partei '' actively engaged in espionage for the '' Abwehr '' , sabotage actions , weapons-smuggling and Nazi propaganda campaigns before the invasion . In late 1939 through spring of 1940 the German '' Volksdeutscher Selbstschutz '' took active part in the massacres of civilian Poles and Jews
massacres of civilian Poles and Jews
Operation Tannenberg
Sonderdienst