The Montana-class battleships will forever remain the ultimate “what if” in the history of the U.S. Navy. Those ships embody a point in time where the ceiling for battleship design was met, right when aerial fighting and aircraft carriers began their era of dominance in naval warfare.
The Montanas were designed during the Second World War as a new generation instead of a mere improvement of the Iowa-class–a family of ships whose speed and firepower were already out of the ordinary. The plan for these new battleships projected them as not only the largest but also the most high-tech ships that the Navy had ever developed. Their tale is big on daring, meticulous craft, and their heritage that is currently only conserved in blueprints and plans rather than on the open waters.
While the Iowa-class centered on speed necessary to keep up with carrier task forces, the Montana-class arm was exchanged for strength and safety. Since there were no treaty restrictions or displacement limits, designers had the liberty to add armor, firepower, and survivability to the maximum by putting the lessons learned from previous naval battles into practice.
The ships would have displaced more than 70,000 tons fully loaded, with a top speed of around 28 knots. This wait allowed the Montanas to equip far thicker armor and heavier guns than the Iowas, thus making them almost invulnerable in traditional surface battles; however, at the cost of speed.
Armor was the central theme in their construction. While the internal belts of the South Dakota- and Iowa-class ships were employed for protection, the Montanas were equipped with a giant external vertical belt going along the entire side of the ship.
Not only was the main belt 16.1 inches thick, but it was also reinforced with specially treated steel and angled at 19 degrees to offer the maximum effective protection. At a close distance, it amounts to about 18 inches of resistance, while the angled design helped in the defense against shells hitting from a steeper trajectory at longer ranges.
As a measure for defense against attack from above, upon the main belt, the Montanas had a secondary lower belt. Five and a half inches thick over the magazines and 7.2 inches over machinery spaces, it covered the area down to the triple bottom of the ship. Thus, it formed a multi-layered network for resisting heavy shells and underwater explosions.
Just as powerful was the system of protection from above. The deck had three layers of armor: a 2.25-inch weather deck that was supposed to deactivate the fuses of the incoming projectiles, a 7.05-inch main deck over the central citadel, and a one-inch splinter deck for stopping fragments. The total thickness of almost 10 inches of horizontal armor offered stout defense against enemy shells as well as aerial bombs.
Not only the main guns but their supporting barbettes too were made strong to endure heavily fought battles. The thickness of turret faces was 22.5 inches—just 3 inches thicker than those on the Iowa-class—with the sides and roof being heavily reinforced. The thickness of the barbettes varied from 18 to 21.3 inches, which was enough for the continuous firing of the main battery even under a heavy bombardment.
Torpedo defense was one of the main concerns of the underwater protection system, consisting of four void layers between the inner bulkhead and outer hull. The two layers closest to the external part of the hull were filled with fluid that served as a cushion for the explosive energy, while the inner two were empty so that the remaining forces could be dissipated. Due to the size of Montana, this system was not only built deeper but also more efficiently than on the previous battleships, thus providing excellent torpedo resistance.
Even though none of the Montana-class battleships were ever brought to completion, the peaks of battleship ambition still echo through their blueprints. For quite a while, these designs represented the zenith of traditional naval warfare as they cleverly blended unheard-of firepower, almost impenetrable armor, and state-of-the-art engineering into one.