Complex sentence: Because of its strategic position, Robert Curthose, son of William the Conqueror, erected a wooden castle there in the year 1080 and the town was henceforth known as "Novum Castellum" or "New Castle".
Split into simpler sentences: Because of its strategic position, Robert Curthose, son of William the Conqueror, erected a wooden castle there in the year 1080. The town was henceforth known as "Novum Castellum" or "New Castle".