Complex sentence: A general named Daphnaeus was elected to lead the Syracusan war effort, while an officer named Dionysius, who had been a cohort of the fallen Hermocrates, was also part of the army command staff.
Split into simpler sentences: A general named Daphnaeus was elected to lead the Syracusan war effort. An officer named Dionysius, who was a cohort of Hermocrates, was also part of the army command staff.