Montana-class battleships are one of the biggest “what might have been” stories of American naval history. They were laid down at a time when the battleship was in its peak form, only to be just moments from becoming obsolete with the advent of the aircraft carrier and submarine in a way that dramatically changed the face of naval warfare.
Built in the early years of World War II to replace the thin and quick Iowa-class, the Montanas were conceived to be the largest, heaviest, and most rugged battleships ever envisioned by America. Their tale is a testimony to grandiose aspirations trashed by the shifting fortunes of war.
Unlike the Iowa-class battleships, which were designed for maximum speed to match fast carrier task forces, the Montana-class was different—sheer toughness and destructive firepower. For the first time in years, naval designers were not constrained by treaty limits or displacement limits, and thus they could design a battleship with survivability as its top priority.
Afloat to the gunwales, the ships would displace over 70,000 tons, losing some speed but offering unmatched protection. At approximately 28 knots, they would have been slower than the Iowas but able to withstand much more abuse.
The Montana-class armor layout was perhaps its most typical feature. Rather than the South Dakota and Iowa classes’ internal belt armor, the Montanas reverted to a more traditional external belt—thicker, simpler to repair, and much more effective. Their main belt was an impressive 16.1 inches thick, supported on an extra inch of hardened steel, and sloped at 19 degrees. This positioned the effective protection closer to 18 inches on incoming shells, becoming increasingly strong at long ranges where shells impact at steeper angles.
Designers also provided for new threats, like diving shells, which might dive below the water level and hit below the main armor belt. The answer to this was the Montanas’ second belt, lower down: 8.5 inches thick over magazines and 7.2 inches over machinery space, well within the hull. This multi-layer approach gave the ships hard protection against both shellfire and underwater explosions, based on years of test and combat experience.
The decks were no less sturdy. The Montana-class had three layers of armor: a 2.25-inch weather deck to explode fuzes or break up incoming shells, a main armored deck 7.05 inches thick to envelop the ship’s internal organs, and a thin splinter deck of approximately an inch to stop fragments. Overall, the horizontal armor totaled almost 10 inches above the citadel—a phenomenal defense against bombs and plunging fire, far thicker than that on the preceding American battleships.
Their main gun turrets and barbettes were equally intimidating. Each turret would have been shielded by a 22.5-inch faceplate, heavier than the Iowa-class, with reinforced roofs and sides. The barbettes—the armored wells below the turrets—were 18 to 21.3 inches thick. These advancements ensured that despite taking it from the enemy, the Montana’s massive guns could still fire, keeping the vessel deadly so long as she floated.
Torpedo defense was also one of the class’s strengths. The Montana-class was advantaged in size because designers were able to include a deep and multi-layered underwater protection system. There were four longitudinal voids spaced along the hull, with the two outer ones to be liquid-filled and the inner two to remain empty and blow off energy. This meant that even if it was hit by an imploding torpedo, the probability of crippling flooding was greatly reduced compared to earlier battleships.
Finally, the Montana-class remained on paper. By the time construction was due to begin, aircraft carriers had proven themselves at sea, and money was directed towards building more carriers, escorts, and submarines.
Still, the design remains an intriguing look at the final chapter of battleship construction—giant floating fortresses that represented the height of naval firepower. Though they never saw the light of day, the Montanas are still symbols of the time when steel, armor, and big guns were still seen as the ultimate expression of sea power.