The Montana-class battleships are the best “what if” in U.S. Navy history. They were a period when battleship engineering was straining at the seams, only to be overtaken by the advent of air power and carriers.
During World War II, designed to replace the Iowa-class, the Montanas were conceived as the largest and most technologically sophisticated battleships the U.S. Navy had ever conceived. Their story is one of bold vision, innovative engineering, and a legacy that has been saved in plans and blueprints and not on the open seas.
While the Iowa-class had emphasized speed to keep up with speedy carrier task forces, the Montana-class reverted to a program of sheer ruggedness. Free from treaty constraints and old displacement limitations, the designers had scope to revisit armor, firepower, and survivability using lessons hard-earned from past battles.
The vessels would have had a loaded displacement in excess of 70,000 tons, at around 28 knots. That was relatively slow compared with the Iowas, but at the expense of some protection and firepower, which would have made the Montanas more nearly invulnerable in the traditional naval battle.
Armor controlled their design. In contrast to the internal South Dakota and Iowa-class belts, which might be complex to service during an engagement, the Montanas had an external vertical belt. The main armored belt was 16.1 inches thick and was supplemented by specially treated steel before being angled at a 19-degree pitch to provide the maximum effective resistance.
At close ranges, this meant about 18 inches of protection, and improved performance at more extended ranges with steeper shell trajectories.
To guard against plunging shells—armour-piercing shells that would be fired from overhead—the Montanas had a second lower belt. Eight and a half inches thick over magazines and 7.2 inches over machinery spaces, the thickness descended to the triple bottom of the ship, providing the layered armour for a well-balanced defence against both heavy guns and underwater bursts.
Horizontal protection was no less strong. Three armors shielded weak points of the deck: a 2.25-inch weather deck to detonate incoming fuzes ahead of time, a 7.05-inch main deck over the central citadel, and a splinter deck of about an inch to stop fragments. Combined, this amounted to nearly 10 inches of horizontal armor—a substantial jump from past battleships and a robust shield against both enemy shells and aerial bombs.
The main gun turrets and their barbettes were also strengthened. The 22.5-inch thick turret faces, three inches more than those of the Iowa class, had sides and roofs that were extremely reinforced. Barbettes supporting these massive guns were between 18 and 21.3 inches thick, giving the ship’s main battery unmatched survivability. In theory, this enabled the Montana-class to continue firing in the face of a steady bombardment without loss of combat capability even in the midst of a naval firefight.
Protection underwater was also well considered. A torpedo defense system with four void layers between the inner bulkhead and outer hull was fitted in the ships. The outer two were filled with fluid to absorb explosive force, and the inner two were hollow to dissipate any residual forces. Because of the ship’s size, this system could be built deeper and more effectively than on older battleships and offered huge resistance to torpedoes.
The Montana-class battleships never went into service, but their blueprints are the apotheosis of battleship ambition—a union of power, armor, and engineering prowess that for one fleeting moment reflected the height of naval warfare theory.