In one of the Germany military's first acts of World War II the German air force, the "Luftwaffe", bombed the Polish town of Wieluń and later went on to bomb cities across the country, including Warsaw, Frampol and various other cities. Collectively the bombings killed tens of thousands of Polish civilians. However, no positive or specific customary international humanitarian law with respect to aerial warfare existed prior to and during World War II which means that at the time, strategic bombings were not officially war crimes. For this reason, no German officers were prosecuted at the post-World War II Allied war crime trials for aerial raids.