During August/October 1944 Warsaw Uprising by the Polish Home Army Hahn fought with the "Waffen-SS", leading a battalion of 700 men in the southern districts of the city and later in the downtown area. He also personally commanded the defense of Warsaw’s heavily fortified government district. Following the capitulation of the uprising, Hahn, acting on instructions from Himmler, ordered the mass-killing of Polish civilians in retaliation for the rebellion. Between August and September of 1944 an estimated 5 to 10 thousand men women and children were shot by the Gestapo, mainly in the ruins of the former General Inspectorate of the Armed Forces. Hahn was awarded the Iron Cross, 1st Class for his service in the Uprising.