Whitehead torpedoes made subdivision a survival requirement

The destroyer's story begins with the older naval use of torpedo for a mine and Whitehead's later self-propelled weapon. Both sought to open an uncontrollable hole below the waterline, but an iron hull did not contribute natural buoyancy in the way a wooden structure did. Watertight subdivision trapped enough air to keep a damaged ship's average density below that of the surrounding water. Torpedo defense therefore became a major influence on internal layout, armor choices, and the ability to survive flooding. Whitehead supplied the weapon, but how a navy should employ it remained a separate problem.