Complex sentence: The police returned to the area but were unable to re-enter, forced to retreat several times with heavy losses, and that evening, they called upon Captain Isaiah Rynders to use his influence to stop the battle.
Split into simpler sentences: The police returned to the area but were unable to re-enter and were forced to retreat several times with heavy losses. That evening, they called upon Captain Isaiah Rynders to use his influence to stop the battle.