Complex sentence: At the same time, the 2nd battalion of 83rd Infantry Regiment was ordered to organise a defensive line along the swampy shores of Trościanica river to cover the eastern flank of the Polish forces in the area of Brześć, some 30 kilometres westward.
Split into simpler sentences: At the same time the 2nd battalion of 83rd Infantry Regiment was ordered to organise a defensive line along the swampy shores of Trościanica river. This was to cover the eastern flank of the Polish forces in the area of Brześć, some 30 kilometres westward.