The Montana-class battleships were conceived of as the final and greatest manifestation of an era in which sea power was quantified in the thickness of armor plates and the crash of giant naval gunfire. They were designed to be the ultimate evolution of American battleship design, warships that would even outdo the legendary Iowa-class with thicker armor and more destructive firepower. But the great vision never got off the drawing board, as the war and the future of ship combat went in another direction.
Early in the twentieth century, agreements between the great naval powers placed rigid constraints on what battleships might be. They specified how heavy the ship could be, how large its guns could become, and how much armor it could have. The Montana-class was intended to finally escape those constraints. They were so large, with beams measuring up to 121 feet, that they could not have traversed the original locks of the Panama Canal, causing planners to look at widening the canal just for them.
The lead two ships were authorized by Congress in 1939, even before America entered the war officially. In contrast to the fast Iowa-class designed to keep pace with speedy carrier groups, the Montanas went against the newer American battleship design philosophy: make them tough, make them powerful, and make them capable of standing and fighting even when receiving the most severe pounding.
If they were built, the Montanas would have had the heaviest armor ever installed on an American battleship. Their armors were designed to brush aside the dreaded 2,700-pound Mark 8 “superheavy” shells, much more menacing than anything the Iowa or South Dakota classes were constructed to withstand.
The primary belt itself stood at 16.1 inches thick, angled for maximum stopping power, with a secondary belt placed below the waterline to offer protection against shells that plunged below the surface. These were overlaid with steel above: a 2.25-inch weather deck, a 7.05-inch main armor deck, and an ultimate splinter deck to prevent fragments. Combined, they were designed to withstand plunging fire and air-dropped armor-piercing bombs.
The Montana class gun turrets would have been the most heavily armored ever constructed by the U.S. Navy. Their faces attained a staggering 22.5 inches thick, three inches thicker than the Iowas, and were covered with barbettes encased in as much as 21.3 inches of armor.
None of the other American battleship designs even approached this degree of protection. The thinking was straightforward: these vessels were to absorb shells from the greatest naval guns on the planet and continue firing.
The armor did not terminate at the waterline. Underneath, the Montanas were supplied with a heavy foer-layered torpedo defense system, switching between liquid-filled and air-filled cells at intervals. This was intended to take the form of some impact of a torpedo or mine blast, dissipating its energy before it could rip into the critical interior of the vessel.
It was one of the most sophisticated underwater protection systems of its time and showed the same philosophy that permeated the entire program: these battleships were constructed to survive.
Ultimately, the Montana class was the battleship developed to its absolute limit, a titanic combination of armor, guns, and survivability that could not be ignored by any foe. But they arrived at the wrong time in history. By the time the plans were complete and building could have commenced, the world’s fleets were already anticipating a new type of power on the waves: the aircraft carrier.
The battleship’s day was done, and the Montanas never emerged from paper into metal. All that is left is their legend, a vision of the battleship that might have been the greatest of them all, but came too late to set sail.