All or nothing ( armor ) All or nothing is a method of armor ing battleship s , which involves heavily armoring the areas most important to a ship while the rest of the ship receives significantly less 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 " . 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 battleship s , starting with the laid down in 1912 . " All or nothing " armor was later adopted by other navies after the First World War , beginning with the Royal Navy in its . Rationale . The logic of the design was simple . If the ship was hit in vital areas ( the ammunition and propellant magazines ; the propulsion plant ; the fire - control and command 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 " all - or - nothing " philosophy of armor design required the rethinking of the ship ’ s design , her armor system and the integration of the ship ’ s design architecture with the armor protection system . With this rethinking of design , naval architects had to examine every system and function of a warship , and determine which functions and systems were critical ( and in what priority ) to the survival and mission accomplishment of the warship . This analysis led to designs in which all vital systems and functions were located in a single area within the hull of the vessel , the armored citadel ; within and beneath which the propulsion plant , communications systems , weapons , ammunition stores , and command & control of the ship resided . Everything else resided outside of this armored citadel . When battle stations were called , the whole crew retreated into this area behind armored bulkheads and armored watertight doors , which were sealed so that each compartment within , and the armored citadel as a whole , were virtually immune to enemy action by any but concentrated and direct attack . The all or nothing system was intended to ensure that battleships could survive against the heaviest armor - piercing shells currently in use , while at the same time being able to carry a powerful armament and retain a useful speed and endurance . This was made possible by dispensing with the large areas of relatively light armor which had been used in previous battleship designs ; the weight saved was used to strengthen the armor protecting the " vitals " of the ship . 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 . In the ideal form of the system , all of a battleship ' s armor would be concentrated to form an armored " citadel " around the ship ' s magazine spaces : an armored box of uniform thickness designed to defend against the largest enemy guns . Save for the turrets , the ammunition hoists , conning tower and part of its steering gear , nothing in the way of armor protected the remainder of the ship . By stripping away the armor from all other parts of the ship the armor of the citadel could be made thicker . The armored citadel can be visualized as an open - bottomed rectangular armored raft with sloped sides sitting within the hull of the ship . From this box , shafts known as barbette s would lead upwards to the ship ' s main gun turrets and conning tower . Through compartmentalization and the redundancy of key systems , any damage done to the ship outside of this armored box would be survivable , and as long as those systems within the box remain intact , the ship could continue to fight . To maximize the thickness of armor available for a given weight it was desirable that the citadel be as small as possible . This was achieved by concentrating the ship ' s main battery in three turrets of triple or even two turrets of quadruple ( quad ) gun mountings , as opposed to World War I battleships which typically had four twin turrets for their large caliber guns ( with " HMS " Agincourt having seven twin turrets ) . In some cases the turrets had an all - forward layout , such as the Royal Navy ' s and the French navy ' s . 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 system s 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 , 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 most important finding of the gunner trials on SMS " Baden " was that the thick medium armor was completely useless against large - caliber shells . As a result , the British navy adopted in the the " all or nothing " armor pioneered by the United States Navy . 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 . In practice . No navy built pure " all or nothing " battleships , although most navies put the theory into use to some degree . Designed and built within the full constraints of the Washington Treaty , the Royal Navy ' s and the French navy ' s came closest to the ideal . The misgivings of building a pure " all or nothing " ship was that these had areas still vulnerable to guns of even modest warships , small arms fire , and blast damage from a ship ' s own guns . For instance , blast damage was to plague the careers of the " Nelsons " , a situation aggravated by the positioning of her guns . It was also considered demoralizing for crew , for example those serving in the secondary batteries , to know that they had no protection . The superstructure , for instance , housed crucial command stations , communications , and radar equipment . Other critical areas such as the rudder , propellers , and bow could not be armored , so damage to these areas could reduce a ship ' s maneuverability and buoyancy . From the on to its , the United States Navy pioneered the all or nothing approach without taking it to its logical conclusion . For example , the US designed its battleships to give the crew additional protection instead of relying only on the armored deck of the citadel . These vessels had three armored decks : a sacrificial armored top deck to decap and set off bombs and shells ; a splinter deck between the top ; and citadel decks to protect the majority of the crew from shell and bomb fragments . In World War II - era battleships and modernized Standard type battleship s , the secondary armament was also in armored turrets , the same type of mounts also found in newer fleet carriers and cruisers , since this was a vital defense against enemy aircraft ( particularly Kamikaze s ) . Regardless of armoring scheme used , battleships still had crucial areas that could not be protected such as the bow , rudder , and propellers ; good examples include " Bismarck " and " Prince of Wales " . The superstructure housing command facilities , communications , and radar also remained vulnerable ; for instance " Tirpitz " suffered extensive topside damage in Operation Tungsten . In action . The battleship versus battleship showdown that all sides planned for never came about , so the benefits of the all or nothing ship ' s design were never fully tested . There were few battleship - to - battleship encounters that took place in the Second World War . In the Atlantic , these included the Battle of Mers - el - Kébir in July 1940 , Battle of Dakar in September 1940 , the Battle of Denmark Strait and Last battle of the " Bismarck " in May 1941 , the Battle of Casablanca in November 1942 , and the Battle of North Cape in 1943 . In the Pacific , there was the Second Naval Battle of Guadalcanal in November 1942 and the Battle of Surigao Strait in October 1944 , part of the larger Battle of Leyte Gulf . In the Battle of Denmark Strait , was hit repeatedly by 15 in ( 38 cm ) AP shells , causing damage without seriously endangering the ship . was built to an early standard and suffered a magazine explosion allowed by poor deck armor . A tilt of the ship towards " Bismarck " in her final turn exposed the deck armor when she made ready to unmask her rear battery . Using the older banded armor design that was geared towards shorter - range fire as in the Battle of Jutland , the Kriegsmarine ' s was well - built and compartmentalised , and proved difficult to sink . " Bismarck " withstood tremendous punishment during her last battle , as an expedition later found out that almost no British heavy shells penetrated the " Bismarck ' s " citadel , although some main - turret barbettes were penetrated . " Bismarck ' s " sister ship " Tirpitz " suffered extensive topside damage from Royal Navy aerial strikes during Operation Tungsten but her vitals were relatively unharmed . In the Second Naval Battle of Guadalcanal ( also known as the fourth battle of Savo Island ) was hit by a 14 in ( 36 cm ) armor - piercing round from the Japanese battleship Kirishima which shattered on a barbette without serious damage . Though " South Dakota " was in no danger of sinking , she was put out of action by faulty circuit breakers as well as damage from smaller caliber fire . The Battle of Surigao Strait was the last battleship versus battleship encounter . Once the Japanese forces ( after first being decimated by US destroyer torpedoes ) reached the main US line , the deciding factor was the much greater numbers of the American forces , plus their superior radar , so the armor scheme of US battleships were not tested .