The Montana-class battleships are still one of the great “what might have been” tales in American naval history. Designed during World War II as the ultimate development of the American battleship, these behemoths were to top the already powerful Iowa-class. They were the pinnacle of dreadnought design—larger, more robust, and more lethal—yet they never made it beyond the drafting board, caught up by the quick transition to carrier-oriented warfare.
While the Iowa-class was focused on high speed to match up with high-speed carrier groups, the Montanas represent a conscious step back toward the Navy’s pre-war doctrine of heavy-armor capital ships. Without treaty limits now and with experience gained in wartime battles, designers set their sights on survivability and firepower over raw speed. Loaded to capacity, these vessels would displace over 70,000 tons, at a speed of about 28 knots—slower than the Iowas but heavily armored and protected far beyond.
The most significant change was the switch back to an external armored belt. Prior classes, such as the South Dakotas and Iowa, had employed internal belt armor, which was troublesome to repair and less effective in some circumstances. Montana’s primary belt was a whopping 16.1 inches thick, supplemented with an additional inch of special treatment steel and inclined at 19 degrees to boost its effective resistance—about equal to 18 inches of vertical armor at close distance, and still more as engagement distances increased.
Designers also responded to the menace of “diving shells”—armor-piercing shells that would strike the water just short of the ship and penetrate below the belt. In response, the Montana-class featured a lower armored belt behind the main one: 8.5 inches on top of ammunition magazines and 7.2 inches on top of machinery spaces. This lower belt went all the way down to the triple bottom, forming a multi-layered defense against plunging shells as well as underwater blasts.
Horizontal protection was also sophisticated. Montana’s deck armor consisted of three layers: a 2.25-inch weather deck to trigger bomb fuzes and dull incoming shells, a 7.05-inch-thick main armored deck to protect the citadel, and a splinter deck up to an inch thick to trap shards. Above vulnerable spaces, this totaled nearly 10 inches of horizontal armor—more than enough to deter both heavy naval artillery and aerial-delivered bombs.
The primary battery weaponry was greatly reinforced as well. Each turret boasted a 22.5-inch faceplate—three inches thicker than the Iowa class—along with thicker side and roof armor. Barbettes that carried the turrets measured 18 to 21.3 inches thick, providing unequalled toughness for the Montana’s big guns. In theory, these battleships could continue to fire even under the worst of enemy salvos.
Underwater, the Montana-class had a deep, multi-layered torpedo defense system. There were four longitudinal compartments along the hull from the outside to the inmost bulkhead: the outer two contained liquid to damp the shock of a blast, and the inner two were evacuated to allow the remaining blast force to disperse. Due to the size of the ships, this system was deeper and more efficient than on any previous U.S. battleship.
The Montana-class was, in all respects, the ultimate expression of American battleship design—monstrous, well-armed, and virtually untakable. But plans were not yet drawn when the era of the battleship was drawing to an end, replaced by the supremacy of the aircraft carrier. The Montanas never existed, leaving historians of the navy to wonder what would have become of these steel giants had they ever set sail.
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