The Montana-class battleship was a class of planned battleships for the United States Navy. The class was designed to replace the Iowa-class battleships. It was not designed to counter the Yamato-class "super battleships" because it was designed before the war started and the United States did not know about the yamato at the time. Five vessels were approved for construction during World War II, but the heavier demand for aircraft carriers resulted in their cancellation before any work could begin.
Planning for the Montana-class battleships commenced in 1939, when the aircraft carrier was still considered inferior to the battleship. The US Navy began designing a 65,000 ton battleship to counter the threat posed by the Imperial Japanese Navy's Yamato-class "super battleships". Although the US Navy had limited knowledge about the Yamato-class, the new Japanese battleships were rumored to have a main gun battery of 18 inches. Initially, US Navy designers drew up plans for a 45,000 ton battleship, but after evaluation, the Battleship Design Advisory Board increased the displacement of the planned ship to 58,000 tons.
At the time, the design board issued a basic outline for the Montana-class ships that called for it to be free of beam restrictions imposed by the Panama Canal, be 25% stronger offensively and defensively than any other battleship completed or under construction, and be capable of withstanding the "super heavy" 2,700 lb shells used by United States Navy's battleships equipped with either the 16 inch Mk. 7 guns. Although freed of the restriction of fitting through the Panama Canal, the length and height of the Montana-class were limited by one of the shipyards at which they were to be built. The New York Navy Yard could not handle the construction of a 58,000 ton ship, and vessels built there had to be low enough to clear the Brooklyn Bridge at low tide.
After debate at the design board about whether the Montana-class should be fast, achieving the high 33 knots speed of the Iowa-class ships, or up gunned and up armored, firepower was selected over speed, which returned the Montana-class to the slower 28 knots top speed of the North Carolina-class and South Dakota-class ships. Armor protection was also increased, enabling the Montana-class ships to withstand enemy fire equivalent to their own. This limited the Montana-class' ability to escort and defend the Pacific based Allied aircraft carrier fleet. Machinery was to be eight Babcock & Wilcox boilers which would have enabled the Montanas to acheive a top speed of approximately 27 to 28 knots.
The Montana-class ships displaced at 65,000 tons standard, and then rose to a total of 70,965 tons under deep load. The ships dimensions were 280.57 meters long, 36.88 meters beam, and 11 meters draught. Machinery was eight Babcock & Wilcox 2 drum express type boilers driving four sets of Westinghouse geared steam turbines, generating a total of 172,000 shaft horsepower, and propelling the ships at a top speed of 28 knots. Under a continuous cruising speed of 15 knots, the Montana-class ships had a predicted range of 15,000 nautical miles. Crew was predicted to numbered at 2,355 for a standard vessel, and any Montana-class ships serving as flagships were predicted to have a crew of 2,789.
The armament of the Montana-class battleships would have been similar to that of the preceding Iowa-class battleships, but with an increase in the number of primary and secondary guns for use in combating enemy surface ships and aircraft. Had they been completed, the Montana-class ships would have been gun for gun the most powerful battleships the United States had constructed, and the only US battleship class that would have come close to equaling the Imperial Japanese Navy's Yamato-class battleships on a gun for gun and ton for ton basis. The primary armament of a Montana-class would have been twelve 16 inch Mk. 7 guns, which would have been mounted in four three gun turrets, two forward and two aft. The guns, the same mounted in the Iowa-class battleships, were 20 meters long – fifty times their 16 inch bore, or 50 calibers, from breechface to muzzle. Each gun weighed about 239,000 lb without the breech, and 267,900 lb with the breech. They fired projectiles weighing up to 2,700 lb at a maximum velocity of 820 meters per second for a distance of up to 28 miles. At maximum range the projectile would have spent almost one and a half minutes in flight. The addition of the fourth turret would have allowed the Montana-class to outgun the Yamato-class having heaviest broadside overall. The Montanas would have had a broadside of 32,400 lb compared to the Yamotos 28,800 lb. Each gun would have rested within an armored barbette, but only the top of the barbette would have protruded above the main deck. The barbettes would have extended either four decks at turrets 1 and 4 and five decks at turrets 2 and 3. The turrets would not have been attached to the ship, but would have rested on rollers, which meant that had any of the Montana-class ships capsized, the turrets would have fallen out, reducing the chance of them pulling the ship under. Each turret would have cost $1.4 million, but this figure did not take into account the cost of the guns themselves. The turrets would have been three-gun, not triple, the reason being that each barrel would have elevated and fired independently. The ships could fire any combination of their main battery, including a full broadside of all twelve. Contrary to popular belief, the ships would not have moved sideways noticeably when a broadside was fired. The guns would have been elevated from less than 5° to more than 45°, moving at up to 12° per second. The turrets would have rotated about 300° at about 4° per second and could even be fired back beyond the beam, which is sometimes called "over the shoulder". Within each turret, a red stripe on the wall of the turret, just inches from the railing, would have marked the boundary of the gun's recoil, providing the crew of each gun turret with a visual reference for the minimum safe distance range. Like most battleships in World War II, the Montana-class would have been equipped with a fire control computer, in this case the Ford Mk 1A ballistic computer, a 3,150 lb rangekeeper designed to direct fire on land, sea, and in the air. This analog computer would have been used to direct the fire from the battleship's big guns, taking into account several factors such as the speed of the targeted ship, the time it takes for a projectile to travel, and air resistance to the shells fired at a target. At the time the Montana-class was set to begin construction, the rangekeepers had gained the ability to use radar data to help target enemy ships and land based targets. The results of this advance were telling. The rangekeeper was able to track and fire at targets at a greater range and with increased accuracy, as was demonstrated in November 1942 when the North Carolina-class battleship USS Washington engaged the Imperial Japanese Navy battleship HIJMS Kirishima at a range of 18,500 yards at night. USS Washington scored at least nine heavy calibre hits that critically damaged Kirishima and led to her loss. This gave the US Navy a major advantage in War, as the Japanese did not develop radar or automated fire control to the level of the US Navy. The large caliber guns were designed to fire two different 16 inch (406 mm) shells. The Mk. 8 APC (Armor-Piercing, Capped) armor piercing shell was used for anti ship and anti structure work, and the Mk. 13 HC (High-Capacity—referring to the large bursting charge) high explosive shell was designed for use against unarmored targets and shore bombardment. The final type of ammunition developed for the 16 inch guns were W23 "Katie" shells. These shells were born from the nuclear deterrence that had begun to shape the US armed forces at the start of the Cold War. To compete with the Air Force and the Army, which had developed nuclear bombs and nuclear shells for use on the battlefield, the Navy began a top-secret program to develop Mk. 23 nuclear naval shells with an estimated yield of 15 to 20 kilotons. The shells entered development around 1953, and were reportedly ready by 1956. However, the cancellation of the Montana-class meant that only the Iowa-class battleships, mounting the same type of gun, could use the shells if the need had arisen.
The secondary armament for the Montana-class ships were to be twenty 5 inch mounted in ten turrets along the vessel's superstructure, five to starboard and five to port. These guns, designed specifically for the Montana-class ships, were to be the replacement for the 5 inch secondary guns then in great use within the United States Navy. The 5 inch gun turrets were similar to other 5 inch gun mounts in that they were equally adept as anti aircraft guns and for damaging smaller ships, but differed in that they weighed more, fired heavier shells, and resulted in faster crew fatigue than other 5 inch guns. The ammunition storage for the 5 inch gun was 500 rounds per turret, and the guns could fire at targets nearly 26,000 yards away at a 45° angle, and at an 85° angle, the guns could hit an aerial target at an altitude of over 50,000 feet. The cancellation of the Montana-class vessels in 1943 pushed back the combat debut of the new 5 inch guns to 1945, when they were used aboard the United States Navy's Midway-class aircraft carriers. The guns proved adequate for the carrier's air defense, but were gradually phased out of use by the carrier fleet because of their weight.
For the first time since the construction of the Iowa-class battleships, the United States Navy was not building a fast battleship class solely for the purpose of escorting Pacific based aircraft carriers, and thus the Montana-class ships would not be designed principally for escorting the fast carrier task forces. Nonetheless they would have been equipped with a wide array of anti aircraft guns to protect themselves and other ships, principally the US aircraft carriers, from Japanese aircraft. The Montana-class were planned to mount ten to forty 40 mm Bofors AA guns and fifty-six 20 mm Oerlikon AA guns.
The Montana-class ships would have been the US Navy's only battleships of World War II to be adequately armored against guns of the same power as their own. The side belt measured 16.1 inches tapering down to 10.2 inches on a 1 inch STS plate inclined at 19°. The lower side belt measured at 7.2 inches tapered to 1 inch inclined at 10°. Torpedo bulkheads measured at 18 inches forward, and 15.25 inches aft. Barbettes measured at 21.3 inches forward, and 18 inches aft. Main turrets measured up to 22.5 inches and decks up to 6 inches.
The Montana-class ships would have also been able to carry three to four aircraft for reconnaissance and for gunnery spotting purposes. The type of aircraft used would have depended on when exactly the battleships would have been commissioned, but in all probability they would have used either the Vought OS2U Kingfisher or the Curtiss SC Seahawk floatplane. The aircraft would have been floatplanes launched from catapults on the ship's aft. They would have then been recovered by crane.
Following the Washington Naval Disarmament Treaties of 1922, and later restrictive naval treaties of the 1930s, the United States Navy found itself in need of more powerful warships, primarily battleships. Carl Vinson, chairman of the House Committee on Naval Affairs, chose to implement the Vinson Naval Plan, which was intended to return the US Navy to it's full fighting strength. In 1938, United States Congress passed the Second Vinson Act to complete the overall plan that had been implemented by Vinson, which cleared the way for construction of the four South Dakota-class battleships and the first two Iowa-class battleships. Four additional battleships were approved for construction in 1940, with the last two intended to be the first of the Montana-class ships. By 1942, it was apparent to the US Navy high command that they needed as many fast battleships as possible, and two more Iowa-class ships were approved for construction as the fast battleships USS Illinois and USS Kentucky.
The Navy, aware of the ongoing construction of the Japanese battleships of the Yamato-class, conceived a 58,000-ton "super battleship" design in 1938. This new class, intended to bare twelve 16 inch (406 mm) guns, was assigned the name Montana and cleared for construction by the United States Congress under the Two-Ocean Navy Act in 1940. Funding for the new ships was approved in 1941. These ships, the last battleships to be ordered by the US Navy, were originally to be designated BB-65 through BB-69. However, BB-65 and BB−66 were subsequently reordered as Iowa-class ships USS Illinois and USS Kentucky, and the Montana-class ships were redesignated BB-67 through BB-71.
Completion of the Montana-class, and the last two Iowa-class battleships, was intended to give the US Navy a considerable advantage over any other nation, or probable combination of nations, with a total of 17 new battleships by the late 1940s. The Montana-class ships would also have been the only American ships to come close to equaling Japan's massive HIJMS Yamato and her sister HIJMS Musashi in terms of size and firepower.
By January 1941, the design limit for the 58,000 ton battleship plan had been reached, and consensus among those designing the battleship class was to increase the displacement to support the armor and weaponry on the ships. At the same time, planners decided to adopt a slightly greater length and reduce power for a better machinery arrangement, as well as improving internal subdivisions, and selecting as the secondary armament several dual mounted 5 inch (127 mm) guns instead of the smaller calibre 5 inch (127 mm) guns used on the Iowa-class ships. At this point, the net design for the Montana-class somewhat resembled the Iowa-class since they would be equipped with the same calibre main guns and similar calibre secondary guns. However, the Montana-class had more armor, mounted three more main guns, and were 6.7 meters longer and 4 meters wider than the Iowa-class ships.
By April 1942, the Montana-class design had been approved. Construction was authorized by the United States Congress and the projected date of completion was estimated to be somewhere between July 1 and November 1, 1945. The US Navy ordered the ships in May 1942, but the Montana-class was placed on hold because the Iowa-class battleships and Essex-class aircraft carriers were under construction in the shipyards required to build the Montana-class ships. Unfortunately for the Montana-class, both the Iowa and Essex classes had been given higher priorities. The Iowa-class had enough speed to keep up with and defend the Essex-class carriers with 20 mm and 40 mm guns, and the Essex-class, because of their ability to launch aircraft to gain and maintain air supremacy over the islands in the Pacific and intercept warships of the Imperial Japanese Navy, all of the Montana-class ships were suspended in May 1942, before any of their keels were laid down. In July 1942, the construction of the Montana-class was cancelled following the Battle of Midway, and the corresponding shift in naval warfare from surface engagements to air supremacy, and, thus, a shift from battleships to aircraft carriers.
Ships in class
- USS Montana (BB-67)
- USS Ohio (BB-68)
- USS Maine (BB-69)
- USS New Hampshire (BB-70)
- USS Louisiana (BB-71)