All or nothing is a method of naval warship armor, best known for its employment on dreadnought battleships. The concept involves heavily armoring the areas most important to a ship while the rest of the ship receives no armor. The "all or nothing" concept avoided light or moderate thicknesses of armor: armor was used in the greatest practicable thickness or not at all, thereby providing "either total or negligible protection".Friedman, Norman. Battleship Design and Development 1905–1945. Conway Maritime Press 1978; , p. 65 Compared to previous armoring systems, "all or nothing" ships had thicker armor covering a smaller proportion of the hull.
The ironclad battleship launched in 1876 had featured a heavily armored central citadel, with relatively unarmored ends; however, by the era of , battleships were armored over the length of the ship with varying zones of heavy, moderate or light armor. The U.S. Navy adopted what was formally called "all or nothing" armor in the Standard-type battleships, starting with the laid down in 1912.Robert Gardiner (Ed.). Conway's All the World's Fighting Ships 1906–1921. Conway Maritime Press, 1985. , 1906–1921, p. 115 The Imperial Japanese Navy soon implemented the system in its battleships starting in 1917, and "All or Nothing" armor was later adopted by other navies after the First World War, beginning with the Royal Navy in its .
Rationale
Traditionally, a warship's armor system was designed both separately from, and after, the design layout. The design and location of various component subsystems (propulsion, steering, fuel storage and management, communications, range-finding, etc.) were laid out and designed in a manner that presented the most efficient and economical utilization of the hull's displacement. Then, armorers would attempt to design the application of barriers and deflectors which would protect vital areas of the hull, the superstructure, and its interior compartments from enemy shellfire, underwater mines, and torpedo attacks. There would also be attention paid to the limiting of sympathetic damage to hull compartments and spaces, caused as a consequence of primary damage to those hull compartments that directly received shellfire or underwater explosions.
The result of this approach was that armorers were "decorating" a warship's hull, interior compartments, and spaces with armor, not according to any overall scheme or protective design. Taken collectively, the total weight of armor yielded by this absence of an overall plan for protection was, in total, far greater than what a realistic hull displacement could float. Consequently, naval architects of the hull and its propulsion system would demand a reduction in the weight of armor applied until the hull displacement and the deadweight of the hull returned the ship's hull form to the range, speed, and stability of the original design performance as specified.
However, the continuing advances of larger-caliber guns, greater muzzle velocities, more accurate fire at longer ranges, and more energetic explosive fills of the shells demanded drastic improvements in armor protection. Some means had to be found to integrate armor protection into the total design of the warship at its inception. The rational application of armor had to achieve the most efficient use of the hull's displacement to provide buoyancy to the deadweight of the ship's armor. "All or nothing" was the design solution.
The "all-or-nothing" philosophy of armor design required the complete rethinking of battleship design, armor systems and the integration of the ship's design architecture with the armor protection system. With the rethinking of design, naval architects had to examine every system and function of a warship and determine the functions and systems that were critical. The systems were assessed as to priority, relationships, and location within the hull and superstructure.
The design was intended to ensure that battleships could (a) survive against the heaviest armor-piercing shells in use in the early part of the 20th century, (b) be able to carry powerful armament, and (c) retain useful speed and endurance. That was made possible by dispensing with the large areas of relatively light armor used in previous battleship designs. The weight saved was used to strengthen the armor protecting the vital areas of the ship, centralized within a compact space. The logic of the design was simple: if the ship were hit in vital areas (the ammunition and propellant magazines; the propulsion plant; the fire-control, command and communications sections), her survival was in jeopardy. On the other hand, if the ship were hit in non-vital areas (non-explosive stores, crew berthing and rest areas, offices and administrative areas), it would most likely not result in the ship's destruction. The armor also strengthened the hull.
In the ideal form of the system, all of a battleship's armor is concentrated to form an armored "citadel" around the ship's magazine spaces. The citadel is an armoured box of uniform thickness designed to defend against the largest enemy guns. The propulsion plant, communications systems, weapons, ammunition stores, and command and control of the ship were located in a single area within and beneath the armored citadel. By stripping away the armor from all other parts of the ship, the armor of the citadel could be made thicker. Save for the turrets, the ammunition hoists, the conning tower and part of the steering gear, nothing in the way of armor protected the remainder of the ship. When battle stations were called, the whole crew retreated into this area behind armored bulkheads and armored, watertight doors.
The citadel can be visualized as an open-bottomed (closed top) rectangular armored raft with sloped sides sitting within the hull of the ship. From the box, shafts known as barbettes would lead upwards to the ship's main gun turrets and conning tower. Although it was desirable for the citadel to be as small as possible, the space enclosed was an important source of reserve buoyancy and helped prevent the ship from foundering when other compartments had flooded. Through compartmentalization and the redundancy of key systems, any damage done to the ship outside this armored box would likely be survivable. As long as those systems within the box remained intact, the ship could continue to fight. In effect, the scheme accepted vulnerability to medium-caliber and high-explosive shells striking the unarmored sections of the hull, in order to improve resistance against large-caliber armor-piercing shells without increasing the overall weight of armor. The unarmored parts of the ship would not offer enough resistance to armor-piercing shells to trigger their firing mechanisms (designed to explode after penetrating armor) so the shells would pass through without exploding, while the vital parts could have armor thick enough to resist the heaviest shells.
To maximize the thickness of armor available for a given weight, it was desirable that the citadel be as small as possible. One way to achieve this was to concentrate the main battery in three turrets of triple or even two turrets of quadruple (quad) gun mountings, as opposed to four twin turrets typical during the First World War. In some cases, the turrets had an all-forward layout, such as the Royal Navy's and the French Navy's . Another way is more compact and efficient machinery such as the French navy's use of "supercharged" Indret boilers for the Dunkerque class or the US Navy's decision to combine double-reduction gear turbines with extreme steam conditions (ultra high heat and pressure) in the , and .
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 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.Friedman, Norman: U.S. Battleships, an illustrated design history. , p. 106. 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 ordnance 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; thus, the maximum thickness of armor would be around the magazine area, leading to the final manifestation of the ‘all or nothing’ scheme.
In practice No navy built pure "all or nothing" battleships, although most navies put the theory into use to some degree. Even Japan's giant was armored along all-or-nothing principles, as there simply was no other way to provide the scale of protection they required. Of the battleships designed and built within the full constraints of the Washington Treaty, the Royal Navy's Nelson class and the French Navy's Dunkerque class came closest to the ideal. Even in these ships some degree of "splinter protection" was included to protect key systems and personnel from fragmentation damage.