Complex sentence: As Earl of Arundel, John vacillated in the conflicts between Henry III and the Barons, and fought on the King's side at the Battle of Lewes in 1264, where he was taken prisoner.
Split into simpler sentences: As Earl of Arundel, John vacillated in the conflicts between Henry III and the Barons. He fought on the King's side at the Battle of Lewes in 1264, where he was taken prisoner.