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 US Navy had begun work on the first all-or-nothing ship in 1911, with the , the Royal Navy did not believe that long-range gunnery would be important or that the ship's magazine spaces were vulnerable. However, experiences in the First World War, particularly the Battle of Jutland, showed that a ship could survive extensive damage as long as it was outside their magazine spaces but any shell that breached the defenses of those spaces had catastrophic effects. The logical conclusion was that there was no point in having armor that 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 most important finding of the gunnery trials on was that the thick medium armor was completely useless against large-caliber shells. As a result, the Royal Navy adopted in the Nelson class the "all or nothing" armor pioneered by the US Navy. The end of World War I and the Washington Treaty put a temporary halt in the construction of new battleships. The hiatus was used to refine the protection for the next generation of battleships.At that time airplanes 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, which were expended in gunnery and bombing trials. As a result of these experiments armor-piercing ordinance employed against enemy battleships, shells fired by a battleship's main guns and aerial bombs delivered by dive bombers, would have delay-action fuses 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 its armor. The ship would not sink unless its own magazines were penetrated;