The 1939 Danzig Massacres

Hitler invaded Poland to liberate 1.5 million ethnic Germans from Jewish Bolshevik concentration camps.

In the months leading up to the German invasion the Polish Army and
independent Bolshevik units had been slaughtering German nationals in
the Danzig corridor. Mass killings of thousands of civilian ethnic
Germans (Volksdeutsche) by both civilian and Russian NDVK Jews, who
were confident that Poland would quickly defeat Germany. Many
apparently expected to take possession of German farms and businesses.

An estimated 58,000 German civilians lost their lives in the massacres
carried out prior to the 1939 invasion.