Complex sentence: He participated in the Battle of Issus commanding troops on the left wing under the authority of Parmenion, later he accompanied Alexander during his journey to the Oracle in the Siwa Oasis where he was proclaimed a son of Zeus.
Split into simpler sentences: He participated in the Battle of Issus, commanding troops on the left wing under the authority of Parmenion. Later he accompanied Alexander during his journey to the Oracle in the Siwa Oasis where he was proclaimed a son of Zeus.