Complex sentence: Russian victories gave their artillery clear line of fire into the suburbs of Czyste and Wola, they also strengthened the morale of Russian soldiers, convinced that the battle was over once Fort 54 fell.
Split into simpler sentences: Russian victories gave their artillery a clear line of fire into the suburbs of Czyste and Wola. They also strengthened the morale of Russian soldiers, who were convinced that the battle was over once Fort 54 fell.