Complex sentence: The list of Norwegian monarchs begins in 872, the traditional dating of the Battle of Hafrsfjord, after which victor Harald Fairhair united many of the Norwegian petty kingdoms; this realm was later to be known as the Kingdom of Norway.
Split into simpler sentences: The list of Norwegian monarchs begins in 872, the traditional dating of the Battle of Hafrsfjord, after which victor Harald Fairhair united many of the Norwegian petty kingdoms into a single kingdom. Harald's realm was later to be known as the Kingdom of Norway.