Iowa-class battleship
The Iowa class was a class of six fast battleships ordered by the United States Navy in 1939 and 1940. They were initially intended to intercept fast capital ships such as the Japanese s and serve as the "fast wing" of the U.S. battle line. The Iowa class was designed to meet the Second London Naval Treaty's "escalator clause" limit of standard displacement. Beginning in August 1942, four vessels,,,, and, were completed; two more, and, were laid down but canceled in 1945 and 1958, respectively, before completion, and both hulls were scrapped in 1958–1959.
The four Iowa-class ships were the last battleships commissioned in the U.S. Navy. All older U.S. battleships were decommissioned by 1947 and stricken from the Naval Vessel Register by 1963. Between the mid-1940s and the early 1990s, the Iowa-class battleships fought in four major U.S. wars. In the Pacific Theater of World War II, they served primarily as fast escorts for s of the Fast Carrier Task Force and also shelled Japanese positions. During the Korean War, the battleships provided naval gunfire support for United Nations forces, and in 1968, New Jersey shelled Viet Cong and Vietnam People's Army forces in the Vietnam War. All four were reactivated and modernized at the direction of the United States Congress in 1981, and armed with missiles during the 1980s, as part of the 600-ship Navy initiative. During Operation Desert Storm in 1991, Missouri and Wisconsin fired missiles and guns at Iraqi targets.
Costly to maintain, the battleships were decommissioned during the post–Cold War drawdown in the early 1990s. All four were initially removed from the Naval Vessel Register, but the United States Congress compelled the Navy to reinstate two of them on the grounds that existing shore bombardment capability would be inadequate for amphibious operations. This resulted in a lengthy debate over whether battleships should have a role in the modern navy. Ultimately, all four ships were stricken from the Naval Vessel Register and released for donation to non-profit organizations. With the transfer of Iowa in 2012, all four are museum ships part of non-profit maritime museums across the US.
Background
The vessels that eventually became the Iowa-class battleships were born from the U.S. Navy's War Plan Orange, a Pacific war plan against Japan. War planners anticipated that the U.S. fleet would engage and advance in the Central Pacific, with a long line of communication and logistics that would be vulnerable to high-speed Japanese cruisers and capital ships. The chief concern was that the U.S. Navy's traditional 21-knot battle line of "Standard-type" battleships would be too slow to force these Japanese task forces into battle, while faster aircraft carriers and their cruiser escorts would be outmatched by the Japanese s, which had been upgraded in the 1930s to fast battleships. As a result, the U.S. Navy envisioned a fast detachment of the battle line that could bring the Japanese fleet into battle. Even the new standard battle line speed of 27 knots, as the preceding and battleships were designed for, was not considered enough and during their development processes, designs that could achieve over 30 knots in order to counter the threat of fast "big gun" ships were seriously considered. At the same time, a special strike force consisting of fast battleships operating alongside carriers and destroyers was being envisaged; such a force could operate independently in advance areas and act as scouts. This concept eventually evolved into the Fast Carrier Task Force, though initially the carriers were believed to be subordinate to the battleship.Another factor was the "escalator clause" of the Second London Naval Treaty, which reverted the gun caliber limit from to. Japan had refused to sign the treaty and in particular refused to accept the 14-inch gun caliber limit or the 5:5:3 ratio of warship tonnage limits for Britain, the United States, and Japan, respectively. This resulted in the three treaty powers, the United States, Britain, and France, invoking the caliber escalator clause after April 1937. Circulation of intelligence evidence in November 1937 of Japanese capital ships violating naval treaties caused the treaty powers to expand the escalator clause in June 1938, which amended the standard displacement limit of battleships from to.
Design
Early studies
Work on what would eventually become the Iowa-class battleship began on the first studies in early 1938, at the direction of Admiral Thomas C. Hart, head of the General Board, following the planned invocation of the "escalator clause" that would permit maximum standard capital ship displacement of. Using the additional over previous designs, the studies included schemes for "slow" battleships that increased armament and protection as well as "fast" battleships capable of or more. One of the "slow" designs was an expanded South Dakota class carrying either twelve 16-inch/45 caliber Mark 6 guns or nine /48 guns and with more armor and a power plant large enough to drive the larger ship through the water at the same 27-knot maximum speed as the South Dakotas. While the "fast" studies would result in the Iowa class, the "slow" design studies would eventually settle on twelve 16-inch guns and evolve into the design for the after all treaty restrictions were removed following the start of World War II. Priority was given to the "fast" design in order to counter and defeat Japan's Kongō-class fast battleships, whose higher speed advantage over existing U.S. battleships might let them "penetrate U.S. cruisers, thereby making it 'open season' on U.S. supply ships". Therefore overwhelming the Japanese battle line was a major driving force in setting the design criteria for the new ships, as was the restricting width of the Panama Canal.For "fast" battleships, one such design, pursued by the Design Division section of the Bureau of Construction and Repair, was a "cruiser-killer". Beginning on 17 January 1938, under Captain A.J. Chantry, the group drew up plans for ships with twelve 16-inch and twenty guns, Panamax capability but otherwise unlimited displacement, a top speed of and a range of when traveling at the more economical speed of. Their plan fulfilled these requirements with a ship of standard displacement, but Chantry believed that more could be done if the ship were to be this large; with a displacement greater than that of most battleships, its armor would have protected it only against the weapons carried by heavy cruisers.
Three improved plans – "A", "B", and "C" – were designed at the end of January. An increase in draft, vast additions to the armor, and the substitution of twelve guns in the secondary battery were common among the three designs. "A" was the largest, at standard, and was the only one to still carry the twelve 16-inch guns in four triple turrets. It required to make. "B" was the smallest at standard; like "A" it had a top speed of 32.5 knots, but "B" only required to make this speed. It also carried only nine 16-inch guns, in three triple turrets. "C" was similar but added to meet the original requirement of. The weight required for this and a longer belt –, compared with for "B" – meant that the ship was standard.
Design history
In March 1938, the General Board followed the recommendations of the Battleship Design Advisory Board, which was composed of the naval architect William Francis Gibbs, William Hovgaard, John Metten, Joseph W. Powell, and the long-retired Admiral and former Chief of the Bureau of Ordnance Joseph Strauss. The board requested an entirely new design study, again focusing on increasing the size of the South Dakota class. The first plans made for this indicated that was possible on a standard displacement of about. could be bought with and a standard displacement of around, which was well below the London Treaty's "escalator clause" maximum limit of.These designs were able to convince the General Board that a reasonably well-designed and balanced 33-knot "fast" battleship was possible within the terms of the "escalator clause". However, further studies revealed major problems with the estimates. The speed of the ships meant that more freeboard would be needed both fore and amidships, the latter requiring an additional foot of armored freeboard. Along with this came the associated weight in supporting these new strains: the structure of the ship had to be reinforced and the power plant enlarged to avoid a drop in speed. In all, about had to be added, and the large margin the navy designers had previously thought they had – roughly – was suddenly vanishing. The draft of the ships was also allowed to increase, which enabled the beam to narrow and thus reduced the required power. This also allowed the ships to be shortened, which reduced weight.
With the additional displacement, the General Board was incredulous that a tonnage increase of would allow only the addition of over the South Dakotas. Rather than retaining the 16-inch/45 caliber Mark 6 guns used in the South Dakotas, they ordered that the preliminary design would have to include the more powerful but significantly heavier 16-inch/50 caliber Mark 2 guns left over from the canceled s and battleships of the early 1920s.
The 16"/50 turret weighed some more than the 16"/45 turret already in use and also had a larger barbette diameter of compared to the latter's barbette diameter of, so the total weight gain was about. This put the ship at a total of – well over the limit. An apparent savior appeared in a Bureau of Ordnance preliminary design for a turret that could carry the 50-caliber guns and also fit in the smaller barbette of the 45-caliber gun turret. Other weight savings were achieved by thinning some armor elements and substituting construction steel with armor-grade Special Treatment Steel in certain areas. The net savings reduced the preliminary design displacement to standard, though the margin remained tight. This breakthrough was shown to the General Board as part of a series of designs on 2 June 1938.
However, the Bureau of Ordnance continued working on the turret with the larger barbette, while the Bureau of Construction and Repair used the smaller barbettes in the contract design of the new battleships. As the bureaus were independent of one another, they did not realize that the two plans could not go together until November 1938, when the contract design was in the final stages of refinement. By this time, the ships could not use the larger barbette, as it would require extensive alterations to the design and would result in substantial weight penalties. Reverting to the 45-caliber gun was also deemed unacceptable. The General Board was astounded; one member asked the head of the Bureau of Ordnance if it had occurred to him that Construction and Repair would have wanted to know what turret his subordinates were working on "as a matter of common sense". A complete scrapping of plans was avoided only when designers within the Bureau of Ordnance were able to design a new 50-caliber gun, the Mark 7, that was both lighter and smaller in outside diameter; this allowed it to be placed in a turret that would fit in the smaller barbette. The redesigned 3-gun turret, equipped as it was with the Mark 7 naval gun, provided an overall weight saving of nearly to the overall design of the Iowa class. The contract design displacement subsequently stood at standard and full load.
In May 1938, the United States Congress passed the Second Vinson Act, which "mandated a 20% increase in strength of the United States Navy". The act was sponsored by Carl Vinson, a Democratic Congressman from Georgia who was Chairman of the House Naval Affairs and Armed Services Committee. The Second Vinson Act updated the provisions of the Vinson-Trammell Act of 1934 and the Naval Act of 1936, which had "authorized the construction of the first American battleships in 17 years", based on the provisions of the London Naval Treaty of 1930; this act was quickly signed by President Franklin D. Roosevelt and provided the funding to build the Iowa class. Each ship cost approximately US$100 million.
As 1938 drew to a close, the contract design of the Iowas was nearly complete, but it would continuously evolve as the New York Navy Yard, the lead shipyard, conducted the final detail design. These revisions included changing the design of the foremast, replacing the original /75-caliber guns that were to be used for anti-aircraft work with /70 caliber Oerlikon cannons and /56 caliber Bofors guns, and moving the combat information center into the armored hull. Additionally, in November 1939, the New York Navy Yard greatly modified the internal subdivision of the machinery rooms, as tests had shown the underwater protection in these rooms to be inadequate. The longitudinal subdivision of these rooms was doubled, and the result of this was clearly beneficial: "The prospective effect of flooding was roughly halved and the number of uptakes and hence of openings in the third deck greatly reduced." Although the changes meant extra weight and increasing the beam by to, this was no longer a major issue; Britain and France had renounced the Second London Naval Treaty soon after the beginning of the Second World War. The design displacement was standard, approximately 2% overweight, when Iowa and New Jersey were laid down in June and September 1940. By the time the Iowas were completed and commissioned in 1943–44, the considerable increase in anti-aircraft armament – along with their associated splinter protection and crew accommodations – and additional electronics had increased standard displacement to some, while full load displacement became.