After the Germans took over the city , they killed 1,200 &ndash; 3,000 Polish civilians , as part of Operation Tannenberg . The event and place of execution became known as the Valley of Death . The murdered included the president of Bydgoszcz , Leon Barciszewski . Fifty Polish prisoners of war from Bydgoszcz were later accused by Nazi '' Sondergericht Bromberg '' summary courts for taking part in " Bloody Sunday " and shot
Operation Tannenberg
Operation Tannenberg
Bloody Sunday (1939)