Complex sentence: Merneptah had to carry out several military campaigns during his reign, in year 5 he fought against the Libyans, who--with the assistance of the Sea Peoples--were threatening Egypt from the West.
Split into simpler sentences: Merneptah had to carry out several military campaigns during his reign. In year 5 he fought against the Libyans, who--with the assistance of the Sea Peoples--were threatening Egypt from the West.