During the invasion of Poland, at the beginning of World War II, on September 1, 1939, Germany carried out air raids on the city. The 15th Infantry Division, which was stationed in Bydgoszcz, fought off German attacks on September 2, but on September 3 it was forced to retreat. During the withdrawal of Poles, as part of the diversion planned by Germany, local Germans opened fire on Polish soldiers and civilians. Polish soldiers and civilians were forced into a defensive skirmish in which several hundred people were killed on both sides. The event, referred to as the "Bloody Sunday" by the propaganda of Nazi Germany, which exaggerated the number of victims to 5,000 "defenceless" Germans, was used as an excuse to carry out dozens of mass executions of Polish residents in the Old Town Market Square and in the Valley of Death.