Complex sentence: In 1944, following their heavy losses during the rear-guard fights during the German withdrawal from Belarus, Dirlewanger's unit (by then a brigade), was used in the suppression of the Warsaw Uprising.
Split into simpler sentences: In 1944, during the German withdrawal from Belarus, Dirlewanger's unit incurred heavy losses in the rear-guard fights. It was used again (by then as a brigade), in the suppression of the Warsaw Uprising.