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Iowa-class battleship

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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 battlecruisers 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 45,000-long-ton (45,700 t) standard displacement. Beginning in August 1942, 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 U.S. Navy. All older U.S. 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 U.S. 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 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.

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 Kongō-class battlecruisers, 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 North Carolina-class and South Dakota-class 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 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, 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 35,000 long tons (35,600 t) to 45,000 long tons (45,700 t).

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 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 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 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 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 were 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 added 75,000 shp (56,000 kW) (for a total of 300,000 shp (220,000 kW)) to meet 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.

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