Complex sentence: The city of Durham, the seat of the Bishop, was not strongly fortified and the rebel earls entered the city on 14 November, with three hundred horsemen, "where they rent and trampled underfoot the English bibles and Books of Common Prayer".
Split into simpler sentences: The city of Durham, the seat of the Bishop, was not strongly fortified. The rebel earls entered Durham on 14 November, with three hundred horsemen, "where they rent and trampled underfoot the English bibles and Books of Common Prayer".