Complex sentence: Falkenhayn had already given up the plan for a counter-offensive near Arras, to reinforce the Russian front and the Second Army with eighteen divisions moved from the reserve and the Sixth Army and by the end of August only one division remained in reserve.
Split into simpler sentences: Falkenhayn had already given up the plan for a counter-offensive near Arras, to reinforce the Russian front and the Second Army with eighteen divisions moved from the reserve and the Sixth Army front. By the end of August only one division remained in reserve.