R L Minks
Sea Classics

Aug 31, 2006 20:00 EDT

Had the Japanese attack on Pearl Harbor not been such a devastating blow to America's Pacific Fleet the odds are that the US Navy would have prevailed in its plan to build the giant, 65,000-ton Montana-class battleships first envisioned in 1939.

Conceived in the pre-war era when the venerable battleship still reigned supreme, at least in the mind of the black shoe Navy, the mighty Montanas were planned to be an add-on extension to the six 45,000-ton lowas then in advanced stages of designing. Though even then the battleship of tomorrow was looked upon more as a powerful bombardment platform than a warship intended for surface engagements, the Navy felt that the colossal 65,000-tonners would at least be on par with the Japanese Yamato class, rumored to have 18-in rifles in great abundance.

The Navy was largely ignorant of the details of the newer Japanese super-dreadnoughts then under construction, but their strategic concepts included other factors beside matching the speed and armament of individual ships. Foremost, they considered that a greater number of battleships would compensate for any deficiency of firepower and that the battleship sailing with a battle force of large aircraft carriers would always be provided with sufficient air superiority.

The single stumbling block of great concern to all Naval planners was the matter of speed. Naval opinion was widely divided on this issue with one school of thought advocating speeds of 33-kts, as with the proposed Iowas, and the other school clearly of the philosophy that more-heavily armed and armored ships of slower speeds in the 27-kt range would be equally, if not more, advantageous. The result, before the basic decision to accept significant increases in displacement, was that in 1940 the Navy prepared an exhaustive series of some 20 preliminary designs for battleships of the 45,000-ton class.

These follow-on "slow battleship" design studies had standard displacements ranging from 41,627-tons to 46,668-tons. All but one of the studies would have mounted 16-in/50 caliber guns in either twin, triple, or quadruple turrets, the one exception being a design with 14-in/50 caliber guns in quadruple turrets.

Battleships, heavily-armed, well-protected, and designed to withstand plunging fire of the heaviest armor-piercing projectiles, seemed to be least affected by the rapid development of aircraft. Even admitting the practicability of accurate bombing in the face of determined resistance, heavy bombs were considered to be certainly less destructive than armor-piercing shells. After evaluating the 45,000-ton "slow battleship" studies prepared in 1939, the Board decided to accept major increases in displacement in order to obtain more desirable characteristics, primarily improved protection. Fifteen preliminary designs were submitted to the Board between March and July of 1940. In marked contrast to the Iowa design, in which speed was a paramount concern, the Montana-class ships were to be well protected, with heavy armament and only modest maximum speed.

* After evaluating the studies, the Board, on 20 August 1940, made several basic decisions regarding the new ships:

* The construction of a group of high-speed capital ships (the Iowa-class) must be given first priority, and the ships completed as soon as possible.

* Treaty limitations on the displacement of all future capital ships are no longer in effect.

* All limitations on the beam of warships be suspended in view of the plans either to enlarge the Panama Canal or to build a wider canal in Nicaragua (no such plans were undertaken).

* The hitting power of 16-in shells has improved so that the defensive characteristics must also be improved.

* These new battleships must be stronger defensively and offensively by 25 percent than any other ships completed or under construction.

* These important characteristics are desired in the new battleships:

a. Improved engineering plant and arrangement.

b. Lessons learned from wartime experiences in the European theater should be incorporated in the design.

c. High speed.

At that time, the Board approved the basic characteristics for the final design of the Montana-class ships.

Length was limited because some ships were to be built at the New York Navy Yard, where the launching ways could not handle a ship of 58,000-tons. Dry dock number 4 there was enlarged so ships could be built in it and floated out, rather than launched conventionally. The length and displacement limitations complicated problems confronting the Preliminary Design Branch. Another snag was the clearance beneath the East River's Brooklyn Bridge, a factor that affected the height of every ship destined to sail into or out of the Brooklyn Naval Yard. In deference to the bridge, the all important forward mast and conning tower had to be designed low so that the Montanas could clear the bridge's center span at mean low tide. This same problem plagued the Essexclass carriers then also in the early stages of construction.

Several design variations were produced late in 1940. Design Study BB67-1, based on preliminary design study BB65-5A, was used as the basis for the development of more-detailed designs. Study BB67-2 satisfied all the requirements outlined by the General Board, but the standard displacement of 61,400-tons far exceeded the desired 58,000-tons. It resulted from errors inherent in the approximate methods used to estimate the displacement of the earlier study, increased requirements, and reports of modification and weight increases in the Iowa-class ships. Weight estimates, based on data for the Iowa, had to be modified as better information on actual weights became available.

The possibility of using a smaller powerplant was first studied in November of 1940. This proved worthwhile because such a powerplant was eventually selected.

Drastic design modifications were necessary to approach the specified displacement while retaining the required speed, armament, and protection. Design study BB67-3 resulted from these alterations. It had an improved hull form similar to that of the Iowa, although length, beam, and draft remained the same as in BB67-2. The primary change was in the propulsion plant, where a reduction to 180,000-shaft-horsepower permitted improvements in the machinery arrangement and better protection against underbottom explosions. This reduced the length of the machinery spaces and contrubuted to reduction in the overall length of the armor box by 12-ft.

Further weight savings accrued from the modification of the after armor belt. The originally rathergenerous distribution of armor was sharply curtailed, and armored tubes were adopted to protect the steeringgear leads. This sharply reduced the armor weight, but left little protection to the reserve buoyancy in the after part of the ship.

The reductions in armor and power resulted in net weight savings of 1800-tons, and the improved hull form reduced the initial costs of the hull structure and powerplant, as well as permitting reductions in operational costs.

The Board ordered the Bureau of Ships to prepare a detailed design study conforming to the characteristics of BB67-3 and urged further modifications to attain the specified 58,000-ton displacement. The Board discussed the reduction of the after waterline belt and the deck armor. Complete deck protection was desired, because improved AP shells and bombs made armor protection mandatory above the propeller shafts. Deck armor would also provide better protection for the steering-gear leads.

By January 1941 there was a general acceptance of a larger displacement than 58,000-tons, a slightly greater length, reduced power for a better machinery arrangement, and improved internal subdivision. A proposal to save weight by using 5-in/38-cal guns instead of the 5-in/54 caliber was rejected. The substitution of 40mm Bofors machine guns for the 1.1-in quadruple machine gun mounts was approved. As a result, major alterations to the proposed basic design characteristics were authorized.

By then the Montana-class, to all intents and purposes, looked on the drawing boards like an up-scaled, overgrown Iowa boasting a lot more beef in the form of unbelievable armor and muscle in the form of twelve 16-in guns. But, aside from general appearance, all similarity stopped between the Iowa and its hefty big brother, the Montana. In overall size, the Montana was only 34-ft longer (887-ft vs. 921-ft), but she was to be much beamier by 13-ft, so beamy that she would not fit through the Panama Canal. This seemingly insignificant fact was to be the cause of much highlevel debate in the Navy and by the General Board as well. Not to be able to squeeze through the Canal locks mandated the need for the Montanas to be sailed around the Horn every time they were to be deployed from east to west, or vice versa. Though the Navy eventually relented on this longstanding rule the spectre of having so large a warship having to traverse an entire continent every time it moved from ocean to ocean seemed logistically and tactically forboding. At the time, it was intended to cut a new wider canal through Nicaragua, but this ambitious plan soon fizzled in the reality of such an awesome undertaking in wartime.

Concurrent with the size debate was the final matter of engine powerplants. A new study, BB-67-4, accepted a shaft horsepower of 172,000 as capable of giving the colossus a maximum speed of 28-kts. Proposals to increase hull length to compensate for reduced power were rejected because a complete timeconsuming design would have been necessary, and it was desired to have construction commence as soon as possible. This study, issued by the Bureau of Ships on 21 March 1941, was approved by the General Board as that to which the Montana-class ships would be built.

The eight boilers were located in individual fire rooms. This added compartmentation reduced possible flooding from underbottom damage. The undesirability of asymmetrical flooding was recognized, but the designers had sufficient confidence in the side protective system and overall stability to revert to longitudinal subdivision of primary engineering spaces amidships.

Armor freeboard was increased from 8- to 9-ft, providing a better chance of side armor protection after underwater damage. Even with increased displacement, the residual freeboard would remain greater than in the original design.

The .50-cal machine guns were replaced by 20mm Oerlikons, which the Bureau of Ordnance estimated to be at least ten times more effective. A proposal to substitute two quadruple 40mm Bofors machine gun mounts for these light machine guns, which would have increased the displacement, was set aside for further study. As late as April 1942, the General Board decided that work on the ships would be continued.

By then the terrible effect of Pearl Harbor had been felt in all quarters of the Navy. Protagonists argued with convincing authority that the day of the battleship was indeed past and that the hard pressed resources of United States industry, namely steel, were solely needed for the hordes of landing craft and smaller warships required to wage a two-ocean war. Building the four lowas in itself was stretching the ship makers to the limits and whispered gossip hinted that the proposed last two lowas, Illinois (BB-65) and Kentucky (BB-66) would be delayed in getting on the stocks.

But the Navy was adamant in its argument about the need for the super-battlewagons. Even as salvage workers desperately tried to clear the rubble at Pearl Harbor, design studies on the Montana went ahead.

Five ships of the class were projected, all to be built in US Navy yards: The Montana (BB-67) and Ohio (BB-68) at Philadelphia, the Maine (BB-69) and New Hampshire (BB-70) at New York, and the Louisiana (BB-71) at Norfolk. Construction was authorized by Congress on 19 July 1940, although, on 19 May, the Navy had already placed order for their construction to the BB67-4 design scheme. Scheduled completion dates varied from 1 July to 1 November 1945.


Main battery: The most noteworthy feature was the addition of a triple 16-in turret aft. The main battery of twelve 16-in/50-cal guns, Mark 7, in four turrets, was the most-powerful ever projected for an American battleship. The equal distribution of firepower fore and aft was an improvement over that of earlier ships. The weight of the main battery salvo, 32,400-lbs, was by far the heaviest ever given an American battleship. The secondary battery of 20 5-in/54-cal guns, Mark 16, in twin mounts, was the most-versatile and powerful dual-purpose gun ever selected for use by the US Navy. It fired a heavier shell at greater range and with a rate of fire similar to that of the effective 5-in/38-cal gun. In the mid-1970s, improved, fully automatic models of the 5-in/54-cal gun were still being mounted on new destroyer-type ships.

Antiaircraft battery: Although the final machine gun armament had not been established, the 32 40mm Bofors machine guns and 20 20mm Oerlikon machine guns projected in June of 1942 were indicative of a powerful defense. In view of the ship's greater length and beam, the machine gun armament probably would have exceeded that of the Iowa class.

Aircraft: Three floatplanes and two fantail catapults were planned. One plane was to be carried on each catapult and one was to be stowed on deck.

Armor protection in these ships was by far the most effective ever projected for an American capital ship. It was calculated to provide an immunity zone for the armored citadel of from 18.000- to 31,000-yds on the basis of the performance of the 16-in/45-cal gun firing a 2700-lb AP shell. Against the older 16-in/45-cal gun firing a 2240-lb AP shell, the immunity zone was calculated to be 16,500- to 34,500-yds.

The damage done by Japanese planes at Pearl Harbor stressed the need for more than adequate deck and citadel armor, plus increased protection at the sides and bottom of the ship. To secure the safety of the citadel its main side belt was comprised of 16-in thick plates ranging down to 8.5-in thickness over the magazines below. The threat of a plunging bomb led to the planned need for deck armor ranging from 12.3-in on the main deck to 1.5-in on the second deck.

The main battery turrets were to have armor 22.5-in thick overall on the sides and 9.5-in thick on the top. The barbettes were likewise protected from 16-in rifle fire at normal distance with steel varying from 18.5- to 21-in thick. Side protection was increased as a result of lessons learned at Pearl Harbor. The first American warships designed to bend elastically under a bomb or torpedo blast, the fourcompartment system utilized a series of armor cushions that were liquid loaded to reduce the damage of the exploding warhead. In theory the energy of the blast would be dissipated by the liquid between the layers of steel armor. The transverse depth of the system amidships was 20.5-ft, but unfortunately this innovative concept was never to meet the test of combat.

By late June 1942, all work on the massive Montana stopped, its designers gradually being reassigned to more pressing needs as the momentum of the war swept over the long debated project. On 21 July 1943, the Montana project was formally cancelled.

Had the Montanas been built, they would have been five of the most-powerful battleships ever to sail. They would have had the mostdevastating armament ever given an American ship and probably could have outgunned the elusive Musashi and Yama to because of the superiority of American fire-control systems. But the very war that created their need also obsoleted them before they could be built.

Though the Navy early on waived the requirement that every US ship had to be capable of passing through the Panama Canal, it was ultimately the matter of speed and priority that saw this promising superdreadnought shunted aside in favor of large numbers of less-powerful warships. The day of the fast fleet carrier had arrived and the Montana's 28-kts would have banished them to the role of amphibious gun-fire support ships. The massive effort required to build any one of them would have robbed the Navy of a halfdozen large cruisers and an equal number of Jeep carriers. The trade-off in manpower, material and funding was simply not worth the effort.

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Source: Sea Classics