All or nothing (armour)
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All or nothing is a method of armoring battleships, originally developed by the US Navy in the first decade of the 20th century. The characteristic of the system was the avoidance of 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".[1] Compared to previous armoring systems, "all or nothing" ships had thicker armor covering a smaller proportion of the hull. "All or nothing" armor was introduced in the US Navy's Nevada class battleships, laid down in 1912,[2] and was adopted by other navies after the First World War, beginning with the Royal Navy in its Nelson class.
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[edit] Rationale
The all or nothing system was intended to ensure that battleships could survive against the heaviest armor-piercing shells currently in use, whilst 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-calibre and high-explosive shells striking the unarmored sections of the hull, in order to secure immunity to armor-piercing shells without increasing the overall weight of armor.
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 ships turrets, the ship's 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 visualised as an open-bottomed rectangular armored raft with sloped sides sitting within the hull of the ship. From this box shafts, known as barbettes, would lead upwards to the ship's main gun turrets and conning tower. Through compartmentalisation and redundant systems, any damage 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 maximise the thickness of armor available for a given weight it was desirable for the citadel to be as small as possible, this being achieved with for example triple and quad turrets and having an all forward layout for the turrets.
[edit] Evolution
The majority of the battleships of pre and Great war 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 calibre 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 ships thin deck armor rather than its well protected sides.
Although the US navy had begun work on the first all or nothing ship USS Nevada in 1911[3] , the Royal Navy did not believe that long range gunnery would be important nor of the vulnerability of the ship's magazine spaces. Experience in the First World War showed that a ship could survive extensive damage as long as this was outside their magazine spaces, however any shell that breached the defences 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 aeroplane 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 former Imperial German Navy ones and these were expended in gunnery and bombing trials.
It 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 ships vitals. If on its way through the ship there was nothing to activate the fuse than 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.
[edit] 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 Nelson class and the French navy's Dunkerque class came closest to the ideal.
The misgivings of building a pure all or nothing ship revolved around fear of damage from the guns of even modest warships, small arms fire, and even vulnerability to sinking through loss of buoyancy and blast damage from a ship's own guns. Indeed, blast damage was to plague the careers of the Nelsons, a situation aggravated by the positioning of her guns. It was also considered demoralising for crew, for example those serving in the secondary batteries, to know that they had no protection.
From the USS Nevada onwards, culminating in its Iowa class, the United States Navy pioneered the all or nothing approach without taking it to its logical conclusion. For example, giving the crew additional protection by armoring the secondary armament, and rather than just rely on the armored deck of the citadel, persisting with having 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.
[edit] In action
The battle fleet against battle fleet action that all sides planned for never came about, so the benefits of the all or nothing ships design was never fully tested. Using the older banded armor design, the Kriegsmarine's Bismarck-class was well-built and compartmentalised, and proved difficult to sink.
The few battleship-to-battleship encounters that took place in the Second World War include naval Battle of Savo Island and the Battle of Denmark Strait. In the second battle of Savo Island USS South Dakota was hit by a 14 in (36 cm) AP round which shattered on a barbette without serious damage. [4] In the Battle of Denmark Strait, HMS Prince of Wales was hit repeatedly by 15 in (38 cm) AP shells, causing damage without seriously endangering the ship. HMS Hood 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 when she made ready to unmask her rear battery.
[edit] See also
[edit] Notes
- ^ Friedman, Norman. Battleship Design and Development 1905-1945. Conway Maritime Press 1978; ISBN 0-85177-135-1, page65
- ^ Robert Gardiner (Ed.). Conway’s All the World’s Fighting Ships, 1906-1921. Conway Maritime Press, 1985. ISBN 0-85177-245-5, 1906-1921, page 115
- ^ Friedman, Norman:U.S. Battleships an illustrated design history ISBN 0-87021-715-1 P106
- ^ Kirishima's hit on South Dakota
[edit] References
- An illustrated guide to battleships and battlecruisers, John Jordan, 1985, Salamander Books.
[edit] External links
- "All or Nothing" Protection article at The Naval Technical Board.
- A Survey of the American "Standard Type" Battleship a comparison of American standard type battleships against those of other nations, at The Naval Technical Board.
- BB59 armor USS Massachusetts site.
