Complex sentence: Before dawn, the commandos landed from ten whaleboats on Cape Nifti, south of the settlement, while the Royal Marines occupied the harbor, after the submarine had made a reconnaissance of the landing point.
Split into simpler sentences: Before dawn, the commandos landed from ten whaleboats on Cape Nifti, south of the settlement, while the Royal Marines occupied the harbor. Previously, the submarine had made a reconnaissance of the landing point.