U.S. Navy Plan Emerald:
Britain’s Drawing-Board Battleships
by Mike Bennighof, Ph.D.
November 2022

At the end of the First World War, Britain’s Royal Navy found itself with the most powerful fleet on the planet. The German High Seas Fleet had been destroyed, but other potential rivals were building new warships that were much more powerful than anything under the White Ensign.

Britain's most powerful warships carried the 15-inch Mark I as their primary armament. A reliable weapon, it had been introduced in 1912 and armed 10 battleships, four battle cruisers and the just-completing new battle cruiser Hood. But already other nations were introducing more powerful weapons.

Nominally an ally of Britain, Japan had suffered few economic or military losses during the war. The Imperial Navy had eight battleships and battle cruisers with 16-inch guns either just completing or under construction. Four more battleships with 16-inch guns and four battle cruisers with even bigger 18-inch guns were planned to be laid down in 1922.

The United States had never formally allied with Britain (or anyone else) during the Great War, but an American squadron had served in the Grand Fleet and Americans fought alongside the British and other Allies for the last year and a half of the war. Yet while Britain's resources went to fighting the German submarine threat, the U.S. Navy continued to build new battleships. Ten battleships and six battle cruisers with 16-inch guns were under construction or just completed, with the Americans also talking about new ships with 18-inch guns.

To maintain her dominance at sea, Britain would need new warships to match these. The series of designs drafted in late 1920 reflected Britain's considerable war experience, along with knowledge gleaned from examinations of interned German battleships and battle cruisers. All of the designs were for very large ships, heavier if not longer than the new battle cruiser Hood. The huge displacement was necessary to provide enough belt armor to protect against 18-inch shellfire plus extensive underwater protection, and to carry at least eight 18-inch guns.

The 18-inch 40-caliber Mark I aboard HMS Furious. The N3 would have carried the even larger 45-caliber Mark II.

All of the proposals came in much too large for Royal Navy requirements, unable to fit existing dockyards even if the Exchequer could have afforded to build them. The Director of Naval Construction ordered them re-cast around 16-inch guns, and in December 1920 accepted the design concept known as G3 (G from the sequence of proposals, 3 indicating triple turrets).

The G3 battle cruisers had protection equivalent to most battleships, with 12 to 14 inches of belt armor only slightly less thick than that in the last two classes of battleships built for the Royal Navy. But the new design incorporated “sloped” armor, inclined outward at 18 degrees to make it effectively thicker than that of the Queen Elizabeth or Revenge classes.

The ships also adopted an American concept known as “all or nothing” protection. Gun turrets had substantial faces and roofs. Thick armor covered the ships’ “citadel” - an area including the engines, boilers, magazines and command centers plus compartments with sufficient buoyancy to assure that the ship could remain afloat if all its other areas were shot to pieces. These other areas had no protection at all - thin armor would serve to set off high-explosive shells but would not stop armor-piercing rounds, and thus would be worse than no protection at all.

When designed in 1908 and 1909, “all or nothing” protection was a radical, untried concept. But experience during the First World War validated the practice - at the extreme ranges at which gunnery combat took place, shells often struck their targets at high angles and plunged through thin deck armor.

Additionally, the new British design had greatly improved underwater protection, much of which had been developed for the battle cruiser Hood. These included “crush tubes,” 8-foot-long, inch-wide steel pipes in the outermost compartments of the torpedo bulge, backed by liquid-filled spaces (fuel oil, replaced by sea water as the oil was used) and finally armored protection. In theory, these measures would absorb the force of a torpedo warhead’s explosion and minimize damage to the ship.

Sir John Fisher’s old dictum that “speed is armor” had been proven false by wartime experience, but the Royal Navy did not want to back off the design speed of 32 knots. Something had to be reduced to bring the ship to a manageable size, and the choice was to reduce the main armament from 18-inch to 16-inch guns.

Battleship Nelson shows off her turret arrangement.

These were placed in three triple turrets, two facing forward and one amidships - none of the main guns faced the stern quarter. For the first time, a British battleship carried its secondary armament - sixteen 6-inch guns - in turrets, with eight dual mounts. Six high-angle 4.7-inch anti-aircraft guns were also to be mounted.

Concentrating the big turrets forward had several advantages - the turrets and their armored barbettes balanced the great weight of the huge engines mounted aft, making the ships less susceptible to “hogging” (bending in the middle) than a long ship like Hood. It reduced the size of the armored citadel, and keeping all the big guns together also would improve the ship’s gunnery as the fall of shot from a salvo would be more compact and easier to correct at long ranges.

Pleased with the design, the Royal Navy accepted the final drafts in August 1921 and placed orders for four of the battle cruisers from private shipyards in October 1921. All four were officially laid down, some construction began and orders were placed for armor, armament and machinery. But the Washington Naval Limitations talks began on 12 November, and six days later the orders came to suspend construction on the new ships. In the midst of a financial crisis, it’s highly unlikely that Britain could have afforded to continue the project anyway and the limitation talks allowed the ships to be used as bargaining chips to reduce the naval power of potential antagonists like Japan and the United States.

The guns and turrets ordered for the battle cruisers, and many design concepts, did finally see use in the new battleships Nelson and Rodney built after the Washington Treaty. British propagandists pushed the idea that the guns were somehow more powerful than other such weapons (thanks to their high velocity) but this claim had little validity and the British found that the barrels wore quickly and drooped after excessive firing. The blast effects were enormous, as some had predicted - Rodney suffered extensive damage to her plumbing and other systems during her engagement with the German battleship Bismarck in 1941, though she was a much smaller ship than the battle cruisers for which the guns had been intended. Both battleships had to have their standard firwood decks replaced with much thicker teak soon after commissioning, as the original wood planking was sucked off the armored backing when the big guns were fired.

At the same time the battle cruiser studies launched in mid-1920, the Royal Navy also looked at a battleship equivalent to carry the same armament but with less speed and hopefully even better protection. Eight of these would have been built, in two classes of four each. The N3 design selected was very similar to the G3 battle cruiser, but accepted a lower speed to retain the 18-inch guns.

They would have been slightly shorter ships, due to a much smaller power plant, with thicker armor though arranged in the same “all-or-nothing” pattern. Like the battle cruisers, the N3 battleships would have carried an exceptionally heavy anti-aircraft armament for the time, but unlike its twin this design finally deleted torpedo tubes.

The main turrets of the smaller battleship Rodney.

The 18-inch guns were enlarged versions of the 16-inch guns planned for the battle cruisers, and would have shared their flaws. The blast effects would have been devastating and possibly have eventually required the ships to be re-fitted with smaller weapons.

No orders were ever placed for the N3 battleships, and though they would have cost less than their battle cruiser equivalents it’s unlikely that the Treasury could have afforded them, either. They served their purpose as bargaining chips at Washington, as the British successfully traded in obsolete early dreadnoughts and vaporware projects like these while the Americans and Japanese put the cutting torches to modern, new dreadnoughts that were on the slipways and in some cases already launched.

In game terms, the two classes are among the most powerful ships the Great War at Sea series has seen. They suffer somewhat by comparison with American or Japanese ships with similar armament thanks to their layout and the lightweight shells thrown by their guns. But their powers of resistance are remarkable, and they can take enormous punishment.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and NASA Journalist in Space finalist, he has published a great many books, games and articles on historical subjects; people are saying that some of them are actually good. He lives in Birmingham, Alabama with his wife and three children. He misses his Iron Dog, Leopold.

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