Complex sentence: The Dukes of Atholl, as massive landowners, were initiators of and primary participants in, the Highland Clearances, the eviction and forced removal of families from their homes, to be replaced by sheep.
Split into simpler sentences: The Dukes of Atholl, as massive landowners, were initiators of and primary participants in, the Highland Clearances. The eviction and forced removal of families from their homes, to be replaced by sheep.