All or Nothing Armor Scheme : What is It?

In 1916, the United States launched the USS Nevada (BB-36). Compared to previous United States battleships, she was revolutionary in many ways. She used triple turrets, turbines, and she was larger than any other battleship. However, she also carried one notable advancement that was revolutionary compared to all other battleships across the globe. This advancement was her unique armor arrangement. She was the first dreadnought to utilize the all or nothing armor scheme. This armor scheme would become the standard in the United States, continuing to see up until the final battleships of the Iowa and Montana classes. Elsewhere, other nations began to see the merit of the scheme and began to use it. What is all or nothing armor and what made it so important in battleship design?

What is All or Nothing Armor?

all or nothing armor scheme

USS Nevada following her modernization during World War II.

Simply put, all or nothing armoring involves encasing the vitals of a warship in the maximum amount or armor while non critical areas receive none. Sections of the ship either have all of the armor or none at all. However, all or nothing armor scheme goes beyond armor and also affects the design of the ship itself.

Previous dreadnoughts were radically different in their armor layouts. Basically, the ship was designed around its guns and propulsion systems. Armor was then added over the majority of the ship. The ship had different levels of heavy, medium, or light armor depending on the importance of what was behind the armor. The system was inefficient and armor was added or subtracted until the ship had the performance that was specified by the builders.

In contrast, the all or noting armor scheme encased the ship’s vitals inside a heavily armored citadel. Propulsion units, the ship’s magazines, and everything else vital to the performance of the warship was placed behind a heavily armored box. The only exception would be the turrets which would be mounted on protected shafts that emerged from the citadel, the barbettes. Ideally, even the ship’s crew was expected to seal themselves into this citadel during combat, keeping them secure as well. This armored box was intended to be invulnerable to the largest guns the enemy was expected to field. By removing the intermediate armor from the non-vital areas of the ship, designers could maximize the thickness of the armored citadel.

The down side of the heavily armored citadel was that it was not hydrodynamic in the slightest. Unarmored bow and stern units helped to streamline the ship and improve its performance. Being unarmored, these components would be at risk of flooding. Designers compensated for this by ensuring the citadel had ample amounts  of reserve buoyancy. Even with the ends flooded, the ship could remain afloat providing the citadel was intact. As armor piercing shells with fuses became common, it was found that the unarmored ends would also prevent the fuses from triggering, allowing the shell to past through the ship without exploding.

The Evolution of the All or Nothing Armor Scheme

The first warship to utilize all or nothing armor was HMS Inflexible in 1888. The ship had a large armored citadel located amidships. She was designed so that even with the bow and stern flooded, the citadel would provide enough buoyancy to keep the ship afloat. She mounted the heaviest armor ever placed on a British warship. The sides of her citadel measured up to 24″ in certain sections. The ship was a radical leap for its time. Indeed, many criticized the ship and spread vicious rumors about the design. No doubt, this was partly responsible for the lack of further development.

Almost three decades later, it was the United States that opted to use all or nothing armor on their Nevada class battleships. It is a common misconception that the Navy actively pursued the use of all or nothing armor. Rather, it was the logical conclusion that came about from multiple weaknesses that naval designers sought to eliminate. With the Nevada class, designers sought to create a design that would be protected at predetermined range where combat was likely to take place. The United States had suspected that increasing gunnery ranges would make horizontal armor (deck, turret tops, etc) more vulnerable. So they sought a comprehensive armor scheme that combined maximum vertical and horizontal armor over the ship’s vitals. The vertical armor was expected to resist enemy shells out to a certain point where horizontal armor would then protect the ship.

The United States turned out to be right in their assumptions. During the Battle of Jutland, longer gunnery meant that the British and German ships experienced many more hits on the decks and turrets. Jutland had also shown that ships could survive great amounts of damage providing that the vitals of the ship were not compromised. Therefore, European navies determined that armor would ideally be focused on the most important parts of the ship.

Post war gunnery tests conducted by England on the German battleship Baden also made it clear that medium armor provided no protection at all against large caliber naval guns. With that in mind, England came to the conclusion that any armor that could not withstand incoming shells was simply wasted weight. This weight would be better used to strengthen the existing armor over the vitals. With this, they had arrived at the same conclusion that the United States had come to some years before.

The Washington Naval Treaty and its halt on new battleship construction allowed designers to spend their time perfecting armor schemes. At this time, the threat of aircraft was becoming apparent and designers had to increase horizontal armor even more. Using data from Jutland and the gunnery tests on Baden, England implemented all or nothing armor into their first post-war battleships, the Nelson class. The Nelson class battleships might have come closest to the ideal all or nothing layout. Not only did they place the maximum amount of armor around the citadel, but they also attempted to reduce the size of the citadel as much as possible. France also followed this unique layout with their Dunkerque and Richelieu class battleships.

Following the Second London Naval Treaty, nearly all nations made a push for the all or nothing armor scheme. The treaty heavily affected most ship design of the period and battleships were no exception. With battleships limited to 35,000 tons, designers had to not let a single ton go to waste. As all or nothing armor allowed designers to squeeze the maximum amount of armor for a given tonnage, it became almost standard for a majority of modern battleships.

Effectiveness of All or Nothing Armor

Of all the battleships lost during World War II, not a single battleship armored on the all or nothing principle was lost due to its citadel being penetrated.

The battleships Yamato and Musashi, the most heavily armored battleships ever built, were lost due to flooding in their bows and other areas outside of the citadel.  The immense amount of water making them unwieldy and unstable long before they were in danger of sinking.

The German battleship Bismarck struck Prince of Wales several times with 15″ shells causing damage. However, the Prince of Wales was never in any danger of sinking.

The all of nothing protection of the battleship USS South Dakota allowed it to withstand 27 shell hits. Most passed through her unarmored sections, causing negligible damage. Two heavy shells that struck her barbette and belt armor were shattered and caused no damage. Indeed, though the ship was put out of action temporarily, she was in no danger of sinking. The first all of nothing dreadnought, USS Nevada further proved the effectiveness of her armor scheme post war. Not only did she survive two atomic bomb explosions, but she was when used as a gunnery target. Despite being shelled by the battleship USS Iowa and two other warships, she remained afloat and required a torpedo to finally sink her.

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Chris Knupp

A student of military history, I am working to make history more interesting and accessible for everyone.

1 Comment

  1. Billy Samples on 10/04/2017 at 12:57 PM

    Thank you. I enjoyed the article very much.

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