All or Nothing (armor) - Evolution

Evolution

The majority of the battleships up through World War I vintage had armor disposed in belts of varying thickness around the hull, concentrating the main thickness at the point where the majority of the enemy shells would impact. The result of long years of experience, these bands of armor were effective protection when ships fought at close range. As the caliber of guns grew and fire-control systems improved, engagement ranges increased, so that a greater number of hits would result from plunging fire against the ship's thin deck armor rather than its well protected sides.

Although the U.S. Navy had begun work on the first all or nothing ship in 1911, with the Nevada, the Royal Navy did not believe that long range gunnery would be important nor of the vulnerability of the ship's magazine spaces. However, experiences in the First World War, particularly the Battle of Jutland, showed that a ship could survive extensive damage as long as this was outside their magazine spaces, but any shell that breached the defenses of these spaces had catastrophic effects. The logical conclusion was that there was no point in having armor which could not stop a shell penetrating into the magazine spaces, and that any armor that did not contribute to this goal was wasted armor.

The end of World War I and the Washington treaty put a temporary halt in the construction of new battleships. This hiatus was used to refine the protection for the next generation of battleships. It was at this time that the airplane and aerial bombs began to make an impact on naval warfare. With the signing of the Washington Treaty the Allies had an excess of old battleships, especially from the former Imperial German Navy. These were expended in gunnery and bombing trials.

In the light of these experiments, it was believed that aerial bombs and the shells from the guns of enemy battleships would be fused to explode only after penetrating into a ship's vitals. If on its way through the ship there was nothing to activate the fuse, then the shell or bomb could pass through the ship without detonating, or if it did detonate, the blast would be outside of its armor. The ship would only sink if its own magazines were penetrated; thus the maximum thickness of armor would be around the magazine area, leading to the final manifestation of the ‘all or nothing’ scheme.