Complex sentence: A man-of-war (also man of war, man-o'-war or simply man) is a type of armed naval vessel that was the most powerful ships from the 16th to the 19th centuries.
Split into simpler sentences: A man-of-war (also man of war, man-o'-war or simply man) is an armed naval vessel. The men-of-war (or men-o'-war) were some of the most powerful ships from the 16th to the 19th centuries.