Complex sentence: Heavier than "Dunkerque"-class battleships with the hull dimensions of the (projected in 1915), they were strongly armored with a belt and deck armor equivalent to the later and battleship classes.
Split into simpler sentences: Heavier than "Dunkerque"-class battleships, they were with the hull dimensions of the (projected in 1915). They were armored with a belt and deck armor equivalent to the later and battleship classes.