Complex sentence: This is called the ejectment of the Saxons from Longdendale in which the Saxon freeman were replaced with a combination of Norman lords and Saxon chieftains loyal to Hugh Lupus.
Split into simpler sentences: This is called the ejectment of the Saxons from Longdendale. This wholesale ejectment saw all of the pre-existing Saxon freeman being replaced with a combination of Norman lords and a new group of Saxon chieftains loyal to Hugh Lupus.