Fast Battleship - The Washington Treaty Era

The Washington Treaty Era

The signatories of the Washington Treaty were the USA, UK, Japan, France and Italy; at that time the only nations in the world with significant battlefleets. As a result, the terms of the Washington Treaty, and the subsequent treaties of London 1930 and London 1936 had a decisive effect on the future of capital ship design.

The treaties extended the definition of capital ship to cover all warships exceeding 10,000 tons standard displacement or carrying guns exceeding 8-inch calibre; imposed limits on the total tonnage of capital ships allowed to each signatory; and fixed an upper limit of 35,000 tons standard displacement for all future construction. These restrictions effectively signaled the end of the battlecruiser as a distinct category of warship, since any future big-gun cruiser would count against the capital ship tonnage allowance. It also greatly complicated the problem of fast battleship design, since the 35,000 ton limit closed off the most direct route to higher speed, as the increasing length-to-beam ratio would have meant a bigger ship.

Evidence of continued interest in high-speed capital ships is given by the fact that, although the signatories of the treaties were allowed to build 16-inch (406 mm) gunned ships as their existing tonnage became due for replacement, most of them passed up the opportunity to do so, preferring instead lighter-armed but faster ships. A British Admiralty paper of 1935 concludes that a balanced design with 16-inch (406 mm) guns would not be possible within the 35,000 ton limit, since it would be either insufficiently armoured or too slow; it is clear that by this date the 23-knot (43 km/h) speed of the Nelsons was considered insufficient. The recommended design (never built) was one with nine 15-inch (381 mm) guns and speed “not less than 29 knots (54 km/h)”.

The 15-inch (381 mm) gunned Littorio and Richelieu classes, built in the 1930s by Italy and France respectively, reflect similar priorities to the British.

Four capital ships of the treaty era were built to displacements appreciably less than the 35,000 limit; the French Dunkerque and Strasbourg, and the German Scharnhorst and Gneisenau. The Dunkerque class was built in response to the German Panzerschiff (or “pocket battleship”) Deutschland. The Panzerschiffe were, in effect, a revival of the late 19th century concept of the commerce-raiding armoured cruiser; long-ranged, heavily armed, and fast enough to evade a conventional capital ship. Likewise, the Dunkerque, can be regarded as a revival of the armoured cruiser’s nemesis, the battlecruiser. With 29-knot (54 km/h) speed and 330 mm (13 inch) guns, she could operate independently of the fleet, relying on her speed to avoid confrontation with a more powerful adversary, and could easily overtake and overwhelm a Panzerschiff, just as Sturdee’s battlecruisers had done to von Spee’s cruisers at the Falkland Islands in 1914. On the other hand, as a member of the line of battle, alongside the elderly and slow dreadnoughts that made up the rest of the French battlefleet, the design would make no sense, since her speed would lose its value and neither her armament nor her protection would be at all effective against a modern 16-inch (406 mm) gunned battleship such as Nelson.

The Scharnhorst and Gneisenau were Germany’s response to the Dunkerques. They were an attempt to redress the inadequacies of the Panzerschiff design in speed, survivability and powerplant (the diesel engines of the Panzerschiffe were unreliable and produced severe vibration at high speed), and used much material assembled for the Panzerschiffe programme (most significantly, the six triple 11-inch (279 mm) gun mountings originally intended for Panzerschiffe D to F). Although much larger than the Dunkerques, the Gneisenaus were also not intended for the line of battle; apart from their insufficient armament, set-piece battles against the vastly more numerous Allied battlefleets had no place in Germany’s strategic requirements. Instead, the two German ships relied throughout their career on their superlative speed (over 32 knots) to evade the attentions of Allied capital ships.

The treaties also allowed the reconstruction of surviving battleships from the First World War, including up to 3,000 tons additional protection against torpedoes, high-altitude bombing and long-range gunnery. In the late 1930s, the Italian and Japanese navies opted for extremely radical reconstructions: in addition to replacing the powerplant in their existing ships, they lengthened the ships by adding extra sections amidships or aft. This had a double benefit; the extra space allowed the size of the powerplant to be increased, while the extra length improved the speed/length ratio and so reduced the resistance of the hull. As a result, both navies realised significant increases in speed; for example the Japanese Ise class was increased from 23 to 25 knots (46 km/h), and the Italian Cavour class from 21 knots (39 km/h) to 27 knots (50 km/h). France, the UK and the US took a less radical approach, rebuilding their ships within their original hulls; boilers were converted to oil-firing or replaced, as were the engines in some cases, but increases in the output of the powerplant were generally canceled out by increases in the weight of armour, anti-aircraft armament and other equipment.

The exception to the European battleship trend was Japan, which refused to sign the Second London Treaty. It rather uncharacteristically settled for a moderate speed of 27 knots (50 km/h), for the sake of heroic level of protection and firepower in the 18.1-inch (460 mm) gunned 64,000 ton displacement Yamato class.

After much debate, the US settled on two 35,000 ton classes, also with a speed of 27 knots (50 km/h), in the North Carolina and South Dakota classes. Due to treaty restrictions, firepower and protection were emphasized first, although both did manage respectable speed increases compared to their WWI contemporaries to be able to operate as carrier escorts. The US signed the Second London Treaty but was quick to invoke an “escalator clause” to up the main battleship caliber from 14-inch (356 mm) to 16-inch (406 mm) as Italy and Japan refused to adopt it. This made the North Carolina a somewhat unbalanced ship, being designed to resist shells from the 14-inch (356 mm) guns that it was originally intended to carry, but being up-gunned during construction. The South Dakota rectified this with protection proof against 16-inch (406 mm) guns. In order to counter the increase in armor weight and stay within tonnage limits, the South Dakota class had to go with a shorter hull to reduce the length of the required protected area, compensating by installing more powerful machinery than the North Carolinas, and this made the ships somewhat cramped. The US also used the treaty's “escalator clause” to order the 45,000 ton, 33-knot (61 km/h) Iowa class after Japan's withdrawal from the treaty. Being free of treaty limitations, the Iowa class had new 16-inch (406 mm) guns with a greater maximum range, and it had even more powerful engines and a lengthened hull for a significantly faster speed over the North Carolinas and South Dakotas.

For half a century prior to laying down, the U.S. Navy had consistently advocated armor and firepower at the expense of speed. Even in adopting fast battleships of the North Carolina class, it had preferred the slower of two alternative designs. Great and expensive improvements in machinery design had been used to minimize the increased power on the designs rather than make extraordinary powerful machinery (hence much higher speed) practical. Yet the four largest battleships the U.S. Navy produced were not much more than 33-knot versions of the 27-knot, 35,000 tonners that had preceded them. The Iowas showed no advance at all in protection over the South Dakotas. The principal armament improvement was a more powerful 16-inch gun, 5 calibers longer. Ten thousand tons was a very great deal to pay for 6 knots.