Complex sentence: The island's dykes were breached by attacks from RAF Bomber Command on October 3,7 and 11, flooding the central part of the island, forcing the German defenders onto the high ground, and allowing the use of amphibious vehicles.
Split into simpler sentences: The island's dykes were breached by attacks from RAF Bomber Command on October 3,7 and 11. This flooded the central part of the island, forcing the German defenders onto the high ground and allowing the use of amphibious vehicles.