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.

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.

[8] 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).

[10] Priority was given to the "fast" design in order to counter and defeat Japan's 30-knot (56 km/h; 35 mph)[11] 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",[12] 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.

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".

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.

[25][26][27] For half a century prior to laying [the Iowa class] down, the US Navy had consistently advocated armor and firepower at the expense of speed.

[44] Although developed for exclusive use by the battleship's guns it is not known if any of the Iowas actually carried these shells while in active service due to the United States Navy's policy of refusing to confirm or deny the presence of nuclear weaponry aboard its ships.

The Iowas' "all-or-nothing" armor scheme was largely modeled on that of the preceding South Dakota class, and designed to give a zone of immunity against fire from 16-inch/45-caliber guns between 18,000 and 30,000 yards (16,000 and 27,000 m; 10 and 17 mi) away.

The torpedo bulkheads were designed to elastically deform to absorb energy and the two outer compartments were liquid loaded in order to disrupt the gas bubble and slow fragments.

[74][75] Iowas' system was also improved over the South Dakotas' through closer spacing of the transverse bulkheads, greater thickness of the lower belt at the triple bottom joint, and increased total volume of the "bulge".

While the design of the Iowas was too far along to adequately address this issue, experience in the Pacific theater eventually demonstrated that high-altitude unguided bombing was ineffective against maneuvering warships.

Initially, the Iowas carried the Vought OS2U Kingfisher[80] and Curtiss SC Seahawk,[80][81] both of which were employed to spot for the battleship's main gun batteries – and, in a secondary capacity, perform search-and-rescue missions.

The plan called for the ships to be rebuilt to include a flight deck and an armament suite similar to that placed aboard the Essex-class aircraft carriers that were at the time under construction in the United States.

[96][97] Charles Myers, a former Navy test pilot turned Pentagon consultant, proposed replacing the turret with vertical launch systems for missiles and a flight deck for Marine helicopters.

[97] Each battleship was overhauled to burn navy distillate fuel and modernized to carry electronic warfare suites, close-in weapon systems (CIWS) for self-defense, and missiles.

[102] The Phalanx system is intended to serve as a last line of defense against enemy missiles and aircraft, and when activated can engage a target with a 20 mm M61 Vulcan 6-barreled Gatling cannon[103] at a distance of approximately 4,000 yards (3.7 km; 2.0 nmi).

It has been alleged by members of the environmental group Greenpeace[105] that the battleships carried the TLAM-A (also cited, incorrectly, as the TLAM-N) – a Tomahawk missile with a variable yield W80 nuclear warhead – during their 1980s service with the United States Navy, but owing to the United States Navy's policy of refusing to confirm or deny the presence of nuclear weaponry aboard its ships, these claims can not be conclusively proved.

At one point, the NATO Sea Sparrow was to be installed on the reactivated battleships; however, it was determined that the system could not withstand the overpressure effects of firing the main battery.

[117] The debate over battleships in the modern navy continued until 2006, when the two reinstated battleships were stricken after naval officials submitted a two-part plan that called for the near-term goal of increasing the range of the guns in use on the Arleigh Burke-class destroyers with new Extended Range Guided Munition (ERGM) ammunition intended to allow a 5-inch projectile fired from these guns to travel an estimated 40 nautical miles (74 km; 46 mi) inland.

These ships are outfitted with an Advanced Gun System (AGS) that was to fire specially developed 6-inch Long Range Land Attack Projectiles for shore bombardment.

[122][N 12] The Iowa class became culturally symbolic in the United States in many different ways, to the point where certain elements of the American public – such as the United States Naval Fire Support Association – were unwilling to part with the battleships, despite their apparent obsolescence in the face of modern naval combat doctrine that places great emphasis on air supremacy and missile firepower.

[131] In part because of the service length and record of the class, members have made numerous appearances in television shows, video games, movies, and other media, including appearances of the Kentucky and Illinois in the anime series Neon Genesis Evangelion,[132] the History Channel documentary series Battle 360: USS Enterprise,[133] the Discovery Channel documentary The Top 10 Fighting Ships (where the Iowa class was rated Number 1),[134] the book turned movie A Glimpse of Hell,[135][136] the 1989 music video for the song by Cher "If I Could Turn Back Time",[137] the 1992 film Under Siege,[138] the 2012 film Battleship,[139] among other appearances.

She conducted a shakedown cruise in Chesapeake Bay before sailing to Naval Station Argentia, Newfoundland, to be ready in case the German battleship Tirpitz entered the Atlantic.

New Jersey completed fitting out and trained her initial crew in the Western Atlantic and Caribbean before transferring to the Pacific Theatre in advance of the planned assault on the Marshall Islands, where she screened the US fleet of aircraft carriers from enemy air raids.

[150] Reactivated in 1982 under the 600-ship Navy program,[151] New Jersey was sent to Lebanon to protect US interests and US Marines, firing her main guns at Druze and Syrian positions in the Beqaa Valley east of Beirut.

Missouri conducted her trials off New York with shakedown and battle practice in the Chesapeake Bay before transferring to the Pacific Fleet, where she screened US aircraft carriers involved in offensive operations against the Japanese before reporting to Okinawa to shell the island in advance of the planned landings.

She became a symbol of the US Navy's victory in the Pacific when representatives of the Empire of Japan boarded the battleship to sign the documents of unconditional surrender to the Allied powers in September 1945.

Decommissioned for the last time 30 September 1991, Wisconsin was placed in the reserve fleet until stricken from the Naval Vessel Register on 17 March 2006, so she could be transferred for use as a museum ship.