During the Second World War, the U.S. Navy operated four of the most powerful warships ever built, the Iowa-class battleships. Despite their commanding size, an even more powerful fleet of battleships was planned: the awe-inspiring Montana-class.
Montana and her four sisters would have been the largest battleships ever for the U.S. Navy but were superseded by aircraft carriers before they were even built.
The Montana-Class Story: The Concept
In 1940 the U.S. Navy battle fleet included fifteen battleships. The combination of the Great Depression, which limited defense spending, and the Washington and London Naval Treaties, which limited the total tonnage of capital ships and armament, meant that the Navy built just two battleships in the 1930s.
Most of the battle fleet consisted of World War I-era battleships. The growing specter of war resulted in the passage of the Two Ocean Navy Act, a law that authorized construction of seven more battleships, including two more of the Iowa-class.
The remaining five battleships, however, would be of a totally new class. The Montana-class was planned as a follow-on to the Iowa fast battleships, the second generation designed and built after the end of the naval treaties.
Both generations exceeded 35,000 tons displacement, the previous treaty limit, and were armed with 16-inch guns, exceeding the 14-inch treaty limit. But while the Iowas simply exceeded previous treaty obligations, the Montanas were to be a spectacular departure, the largest warships ever for the U.S. Navy.
The Montana specifications made a list of superlatives. Each Montana would have been 921 feet long, sixty one feet longer than their predecessors and 59 feet longer than Japan’s vaunted Yamato class “super battleships”. The new battleships were also wider, with a beam of 121 feet versus 108 feet for the Iowas.
The vast ships would displace 70,965 tons fully loaded, nearly as much as the Yamato-class.
Unloaded one would have displaced a little less than the postwar USS John F. Kennedy, the last American conventionally powered aircraft carrier.
Steam turbines with a total output of 172,000 horsepower would drive the ship at speeds of up to 28 knots.
A Powerhouse Warship Like No Other
Armament was unprecedented for a US battleship and arguably the heaviest ever installed on any battleship ever. The Iowa battleships were armed with nine Mark 7 16-inch, 50 caliber guns mounted in three turrets of three guns each.
The Montana-class would use the same guns but add a second main gun turret aft, for a total of four turrets of three guns each. While the Yamato-class mounted larger, more powerful 18-inch guns, that only told part of the story: not only did a Montana class battleship have twenty-five percent more guns, the smaller, lighter Mark 7 gun could also more rapidly, at a rate of one round every two minutes.
The battleship’s secondary armament was the Mark 16 5-inch dual-purpose gun. The twenty 5-inch guns were envisioned both as anti-surface armament, useful against enemy warships and shore targets, but also as the big ship’s primary long-range anti-aircraft armament.
This was the same number as the Iowa-class, but the guns had 54 caliber barrels, as opposed to 38 caliber barrels on the older battleships. This greater length, nearly seven feet, gave the guns added velocity and range. Armament was rounded out with thirty-two 40mm Bofors guns and twenty 20mm Oerlikon guns, the standard light anti-air weapons of all US Navy warships at the time, even submarines.
A Battleship-Killer
Montana and her sisters were designed to compete and fight with other battleships, and engineers placed an emphasis on armoring against enemy main guns.
Armor protection for the Montanas would have been greater than her predecessors, with a 16.1 inch belt of steel protecting the hull, augmented by a one inch layer of specially treated steel.
A nineteen-degree slope gave it a relative total thickness of 18 inches. Turret armor was up to 18 inches at the frontal arc, with other arcs greater or equal to those on the Iowas.
Critical spaces, including main gun magazines and machinery, received additional protection. Passive protection against detonations below the waterline, including torpedoes and mines, included empty and liquid-filled bulkhead spaces, designed to dampen underwater shockwaves.
Image of Iowa-class Battleships. Image Credit: Creative Commons.
Montana Battleship Plans: Here Comes the Aircraft Carrier
The Navy planned to build five Montanas: Montana, Ohio, Maine, New Hampshire, and Louisiana. Two were to be built at the Philadelphia Naval Yard, two at the New York Naval Yard, and one at Norfolk. Yet by 1942, no keels had been laid down for any of them, and the five battleships were all canceled in 1943. What happened?
By 1940, it was evident that the battleship was giving way to the aircraft carrier as the dominant platform at sea. While the Two Ocean Navy Act authorized seven battleships, including the five Montanas, it authorized a further eighteen aircraft carriers.
USS Iowa (BB-61) Fires a full broadside of nine 16/50 and six 5/38 guns during a target exercise near Vieques Island, Puerto Rico, 1 July 1984. Photographed by PHAN J. Alan Elliott. Note concussion effects on the water surface, and 16-inch gun barrels in varying degrees of recoil. Official U.S. Navy Photograph, from the the Department of Defense Still Media Collection.
The attack on Pearl Harbor on December 7th, 1941, was the final nail in the battleship’s coffin, and the remaining ships were relegated to using their big guns to support amphibious landings and their anti-aircraft armament to protect carriers. USS Wisconsin, commissioned in 1944, would be the last battleship built for the Navy.
The Sad Story of the Montana-Class
The Montana-class was proof the Navy could think big when it came to warships, but placing a priority on aircraft carrier construction and eventually canceling the class altogether was proof the Navy understood that the time of the battleship was over.
Had the ships been built, nothing would have been achieved except bragging rights. While Japan built larger battleships, neither Yamato nor Musashi lasted the duration of the war and contributed very little to the war effort in their time above water.
The Nos. 1 and 2 Mark 7 16-inch/50-caliber guns are fired to starboard during a main battery firing exercise aboard the battleship USS NEW JERSEY (BB-62).
By being canceled and freeing up resources for more urgently needed ships, the Montanas arguably contributed more to the war than their Japanese counterparts.
About the Author: Kyle Mizokami
Kyle Mizokami is a writer on defense and security issues and has been at Popular Mechanics since 2015. If it involves explosions or projectiles, he’s generally in favor of it. Kyle’s articles have appeared at The Daily Beast, U.S. Naval Institute News, The Diplomat, Foreign Policy, Combat Aircraft Monthly, VICE News, and others. Kyle is also a Contributing Editor for 19FortyFive. He lives in San Francisco.
