Iowa Class Battleships

## 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 *Kongō* class while also being capable of serving in a traditional battle line alongside slower battleships and act as its "fast wing". The *Iowa* class was designed to meet the Second London Naval Treaty's "escalator clause" limit of 45,000-long-ton (45,700 t) standard displacement. Four vessels, *Iowa*, *New Jersey*, *Missouri*, and *Wisconsin*, were completed; two more, *Illinois* and *Kentucky*, 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 US Navy. All older US battleships were decommissioned by 1947 and stricken from the *Naval Vessel Register* (NVR) by 1963. Between the mid-1940s and the early 1990s, the *Iowa*-class battleships fought in four major US wars. In the Pacific Theater of World War II, they served primarily as fast escorts for *Essex*-class aircraft carriers of the Fast Carrier Task Force and also shelled Japanese positions. During the Korean War, the battleships provided naval gunfire support (NGFS) 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 16-inch (406 mm) guns at Iraqi targets.

Costly to maintain, the battleships were decommissioned during the post-Cold War draw down 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 NGFS 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 part of non-profit maritime museums across the US.

## Background

The vessels that eventually became the *Iowa*-class battleships were born from the US Navy's War Plan Orange, a Pacific war plan against Japan. War planners anticipated that the US 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. The chief concern was that the US Navy's traditional 21-knot battle line would be too slow to force these Japanese task forces into battle, while faster carriers and their cruiser escorts would be outmatched by the Japanese *Kongō*-class battlecruisers, which had been upgraded in the 1930s to fast battleships. As a result, the US Navy envisioned a fast detachment of the battle line that could bring the Japanese fleet into battle. Even during the development process of the preceding *North Carolina*-class and *South Dakota*-class battleships, 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 14 inches (356 mm) to 16 inches (406 mm). 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, United States, and Japan respectively. This resulted in the three treaty powers, the United States, Britain, and France, invoking the 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 35,000 long tons (35,600 t) to 45,000 long tons (45,700 t).

## 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 45,000 long tons (45,700 t). Using the additional 10,000 long tons (10,200 t) over previous designs, the studies included schemes for 27-knot (50 km/h; 31 mph) "slow" battleships that increased armament and protection as well as "fast" battleships capable of 33 knots (61 km/h; 38 mph) 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 18-inch (457 mm)/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 Dakota*s. 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 60,500-long-ton (61,500 t) *Montana* class 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 30-knot (56 km/h; 35 mph) *Kongō*-class battlecruisers, 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", and then overwhelm the Japanese battle line was therefore 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 5-inch (127 mm) guns, Panamax capability but otherwise unlimited displacement, a top speed of 35 knots (65 km/h; 40 mph) and a range of 20,000 nautical miles (37,000 km; 23,000 mi) when traveling at the more economical speed of 15 knots (28 km/h; 17 mph). Their plan fulfilled these requirements with a ship of 50,940 long tons (51,760 t) 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 8-inch (200 mm) 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 6-inch (152 mm) guns in the secondary battery was common among the three designs. "A" was the largest, at 59,060 long tons (60,010 t) standard, and was the only one to still carry the twelve 16-inch guns in four triple turrets (3-gun turrets according to US Navy). It required 277,000 shp (207,000 kW) to make 32.5 knots (60.2 km/h; 37.4 mph). "B" was the smallest at 52,707 long tons (53,553 t) standard; like "A" it had a top speed of 32.5 knots, but "B" only required 225,000 shp (168,000 kW) to make this speed. It also carried only nine 16-inch guns, in three triple turrets. "C" was similar but it added 75,000 shp (56,000 kW) (for a total of 300,000 shp (220,000 kW)), to make the original requirement of 35 knots (65 km/h; 40 mph). The weight required for this and a longer belt – 512 feet (156 m), compared with 496 feet (151 m) for "B" – meant that the ship was 55,771 long tons (56,666 t) 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 (then president of New York Shipbuilding), 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 35,000-long-ton (36,000 t) *South Dakota*-class. The first plans made for this indicated that 30 knots (56 km/h; 35 mph) was possible on a standard displacement of about 37,600 long tons (38,200 t). 33 knots (61 km/h; 38 mph) could be bought with 220,000 shp (160,000 kW) and a standard displacement of around 39,230 long tons (39,860 t), which was well below the London Treaty's "escalator clause" maximum limit of 45,000 long tons (45,700 t).

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 2,400 long tons (2,440 t) had to be added, and the large margin the navy designers had previously thought they had – roughly 5,000 long tons (5,080 t) – was suddenly vanishing. The draft of the ships was also allowed to increase, which enabled the beam to narrow and thus reduced required power (since lower beam-to-draft ratio reduces wave-making resistance). 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 10,000 long tons (10,200 t) would allow only the addition of 6 knots (11 km/h; 6.9 mph) over the *South Dakota*s. Rather than retaining the 16-inch/45 caliber Mark 6 guns used in the *South Dakota*s, 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 *Lexington*-class battlecruisers and *South Dakota*-class battleships of the early 1920s.

The 16"/50 turret weighed some 400 long tons (406 t) more than the 16"/45 turret already in use and also had a larger barbette diameter of 39 feet 4 inches (11.99 m) compared to the latter’s barrette diameter of 37 feet 3 inches (11.35 m), so the total weight gain was about 2,000 long tons (2,030 t). This put the ship at a total of 46,551 long tons (47,298 t) – well over the 45,000-long-ton (46,000 t) limit. An apparent savior appeared in a Bureau of Ordnance preliminary design for a turret that could carry the 50-caliber guns while also fit in the smaller barbette of the 45-caliber gun turret. Other weight savings were achieved through thinning some armor elements and substituting construction steel with armor-grade Special Treatment Steel (STS) in certain areas. The net savings reduced the preliminary design displacement to 44,560 long tons (45,280 t) 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 back 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 850 long tons (864 t) to the overall design of the *Iowa* class. The contract design displacement subsequently stood at 45,155 long tons (45,880 t) standard and 56,088 long tons (56,988 t) 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 *Iowa*s 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 1.1-inch (27.9 mm)/75-caliber guns that were to be used for anti-aircraft (AA) work with 20 mm (0.79 in)/70 caliber Oerlikon cannons and 40 mm (1.57 in)/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 1 foot (0.30 m) to 108 feet 2 inches (32.97 m), 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 45,873 long tons (46,609 t) standard, approximately 2% overweight, when *Iowa* and *New Jersey* were laid down in June and September 1940. By the time the *Iowa*s 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 47,825 long tons (48,592 t), while full load displacement became 57,540 long tons (58,460 t).

## Class Overview

### Builders

New York Naval Shipyard(BB-61 & BB-63)Philadelphia Naval Shipyard(BB-62, BB-64, & BB-65)Norfolk Naval Shipyard(BB-66)

## General Characteristics

### Displacement

48,110 long tons (48,880 t) (standard)57,540 long tons (58,460 t) (full load)60,000 long tons (61,000 t) (full load) (New Jersey 1968)

### Length

860 ft (262.13 m) (pp)887 ft 3 in (270.43 m) (oa)

### Draft

37 ft 2 in (11.33 m) (full load)37 ft 9 in (11.51 m) (maximum)41 ft (12.50 m) aft, 39 ft (11.9 m) forward (New Jersey 1968)