During the German invasion of Poland, the Luftwaffe engaged in massive air raids against Polish cities,Bruno Coppieters, N. Fotion, eds. (2002) Moral constraints on war: principles and cases, Lexington Books, p 74. bombing civilian infrastructureBob Golan, Jacob Howland, Bette Howland, (2005). A long way home, University Press of America, p 11. such as hospitalsSylwia Słomińska, "Wieluń, 1 września 1939 r." , Z dziejów dawnego Wielunia "History of old Wielun", site by Dr Tadeusz Grabarczyk, Historical Institute at University of Lodz, and targeting fleeing refugees.Norman Davies. (1982). God's Playground: A History of Poland, Columbia University Press, p 437.George Topas, (1990). The iron furnace: a Holocaust survivor's story, University Press of Kentucky, p 23.Hempel, Andrew. (2000). Poland in World War II: An Illustrated Military History p 14.Hooton 1994, p. 183. Notably, the Luftwaffe bombed the Polish capital of Warsaw, and the small towns of Wieluń and Frampol. The bombing of Wieluń, one of the first military acts of World War II and the first major act of bombing, was carried out on a town that had little to no military value. Similarly, the bombing of Frampol has been described as an experiment to test the German tactics and weapons effectiveness. British historian Norman Davies writes in Europe at War 1939–1945: No Simple Victory: "Frampol was chosen partly because it was completely defenceless, and partly because its baroque street plan presented a perfect geometric grid for calculations and measurements."
