By summer 1942, deportations were systematic across those parts of Europe occupied by the Nazis. The convoys which arrived in Auschwitz-Birkenau came from Poland, but also from western and southern Europe. Hitler issued an order for all Polish Jews to be killed before December 1942. The pace of deportations once again picked up, and the children from the ghetto of Lodz were deported starting from early September. The death camps had to be reorganized to deal with the greater number of people. But the war was changing - the Soviet victory in Stalingrad and things were starting to tip in the Allies' favour. Himmler ordered the units of Special Action 1005 - which had been responsible since 1942 for disposing of evidence of the mass shootings which had accompanied Operation Barbarossa in the summer of 1941 - to erase all trace of the genocide in the extermination camps.