Complex sentence: In September 1066 Harold defeated and killed King Harald Hardrada of Norway at the Battle of Stamford Bridge, and Harold was himself defeated and killed the following month by William the Conqueror at the Battle of Hastings.
Split into simpler sentences: In September 1066, Harold defeated and killed King Harald Hardrada of Norway at the Battle of Stamford Bridge. The following month, Harold was himself defeated and killed by William the Conqueror at the Battle of Hastings.