Complex sentence: By 21 December 1944 the Red Army had drawn close enough that orders were issued for Auschwitz to be totally evacuated; it was Schmauser who followed Heinrich Himmler's order to expedite the camp's inmates away as he was in charge in Silesia.
Split into simpler sentences: By 21 December 1944 the Red Army had drawn close enough that orders were issued for Auschwitz to be totally evacuated. It was Schmauser who followed Himmler's order to expedite the camp's inmates away as he was in charge in Silesia.