The September Campaign was an instance of total war. Consequently, civilian casualties were high during and after combat. Apart from the victims of the battles, the German forces are credited with the mass murder of several thousands of Polish POWs and civilians. Also, during Operation Tannenberg, nearly 20,000 Poles were shot at 760 mass execution sites by special units, the Einsatzgruppen.
Altogether, the civilian losses of Polish population amounted to about 150,000-200,000 while German civilian losses amounted to roughly 3,250 (including 2,000 who died fighting Polish troops as members of a fifth column).