Bloody Sunday (; ) was a series of killings against the German minority that took place at the beginning of World War II. On September 3, 1939, two days after the beginning of the German invasion of Poland, highly controversial killings occurred in and around Bydgoszcz (), a Polish city with a sizable German minority. The number of casualties and other details of the incident are disputed among historians. The Nazis exploited the deaths as grounds for a massacre of Polish inhabitants after the Wehrmacht captured the town.