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March 5, 2026 3:49 am
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Project Katie: Nuclear Naval Battles?
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Project Katie: Nuclear Naval Battles?

Tank WilliamsBy 9 Mins Read

The nuclear arms race began during World War II, with the United States and the U.S.S.R. competing for supremacy for decades after the war’s end. Eventually, several other countries joined in, creating nukes for their own protection from their enemies. However, no country could match the scale of nuclear development of the U.S. and the U.S.S.R. superpowers.

Nuclear-armed battleships were designed to deliver devastating strikes against enemy forces and installations. The Mark 23 shells gave these WWII-era vessels a new lease on life as atomic weapons platforms.

After the U.S. destruction of Nagasaki and Hiroshima through the development of nuclear weapons as part of the Manhattan Project, the Soviet Union’s nuclear program went into high gear. While it was thought the Soviets would not be able to create a bomb for several years, they were able to complete their version of the Fat Man bomb, the RDS-1 (also known as the Joe-1 by the Allies in reference to Joseph Stalin) in 1949 due to espionage within the Manhattan Project.

A powerful photograph captures the USS New Jersey battleship firing a salvo from its massive 16-inch Mark 7 guns off the coast of Beirut, Lebanon on January 9, 1984, with enormous muzzle flashes and smoke erupting from multiple gun barrels simultaneously. Mark 7 guns previously fired Mark 23 nuclear shells. Project Katie armed New Jersey with atomic projectiles. USS New Jersey received 1982 modernization upgrades. Battleships carried both conventional and nuclear weapons. Iowa-class vessels deployed serious firepower capabilities. Mark 160 Fire Control systems guided gun operations. New Jersey carried 32 Tomahawk cruise missiles. Naval gunfire supported Lebanon operations effectively.
USS New Jersey (BB-62) fires a salvo from her main guns during a deployment off the coast of Beirut, Lebanon, in January 1984. Image: PH1 Ron Garrison/U.S. Navy

In the 1950s, civilian views on nuclear weapons were a combination of fear and patriotism. Many Americans lived in fear of nuclear war with the Soviets, and the concerns of the long-term effects of radiation exposure was also high, prompting people to construct fallout shelters and stockpile food and supplies.

The Navy Needs a Nuke?

As a result of this arms race, the U.S. military had a prodigious amount of nuclear weapons. The U.S. Army had the Davy Crockett recoilless smoothbore gun, the Special Atomic Demolition Munition, aka the backpack nuke, the Honest John medium-range missile, and atomic cannons with nuclear artillery shells.

A photograph shows a large 16-inch practice artillery shell positioned at the breech opening of a naval gun, demonstrating the loading process used on battleships. Mark 23 nuclear shells required careful breech loading procedures. Project Katie training utilized practice projectiles extensively. Naval gun crews loaded rounds weighing nearly one ton. The Mark 7 gun system fired various shell types. Battleship turrets employed 79-man operating crews. Practice ammunition prepared gunners for nuclear round handling. Each ship maintained nine training shells onboard. Loading drill rounds certified gunner crew proficiency.
A practice round is shown as it would be loaded in the breech. A shell is inserted first, followed by 6 90-pound bags of powder loaded into silk bags. Image: U.S. Navy

The U.S. Air Force had the Mark 4 and B43 gravity bombs, the Atlas ICBM, and, starting in the early 60s, the Titan II ICBM equipped with a single nine megaton warhead.

A photograph shows the interior shell deck beneath a 16-inch gun turret on USS New Jersey, displaying the confined metal-walled space where large artillery projectiles were stored and handled by crew members before being loaded into the guns above. Mark 23 nuclear shells moved through turret levels. Project Katie required secure projectile handling procedures. Shell decks staged ammunition before gun loading. USS New Jersey carried ten Mark 23 projectiles. Projectile handling floors connected magazines to guns. Naval crews worked in cramped turret spaces. Each turret required 79 personnel for operations. Nuclear shells weighed between 1,500-1,900 pounds.
View of the shell deck below a turret on the USS New Jersey. Image: Mark C. Olsen/N.J. Dept. of Veterans Affairs

The U.S. Navy had the Polaris submarine-launched ICBM and the Regulus cruise missile for surface vessels and submarines. Additionally, the Navy employed a number of aircraft, including the Douglas A-3 Skywarrior strategic bomber, capable of delivering a nuclear strike. The only weapon system without a nuke was the U.S. Navy’s big guns on the powerful Iowa-class battleships, but that would soon change.

The Mark 7

The main armament of the Iowa-class battleships, the remarkable Mark 7 gun weighed 267,900 pounds, with the breech. The fired shells weighed between 1,900 and 2,700 pounds. When firing armor-piercing rounds, their muzzle velocity was 2,500 feet per second. When fired at its maximum range of 24 miles, the shell spent almost one minute and 30 seconds in flight.

A technical diagram illustrates the cross-section of an Iowa-class battleship turret showing three large Mark 7 guns with their internal mechanisms, ammunition handling systems, and crew stations across multiple deck levels. Mark 7 guns fired Mark 23 nuclear projectiles. Project Katie required turret system modifications. Naval gun turrets housed complex loading machinery. Three-gun configurations allowed independent gun elevation. Battleship armament weighed nearly 268,000 pounds per gun. Nuclear shells traveled through projectile handling floors. Magazine levels stored atomic artillery components. Turret crews operated four-level gun systems.
This diagram shows a typical Iowa-class battleship with its three independently elevating Mark 7 guns. Image: U.S. Navy

The turrets were described as “three-gun” rather than “triple” because each gun could be elevated or lowered independently of the others. The battleships could fire any combination of their guns, including a broadside of all nine. From the powder-handling level to the magazines, the projectile handling floor, and the gun deck, each turret required 79 men to staff all four levels.

Project Katie

The origin of the “Katie” shell dates back to 1952, when the world’s first artillery-fired atomic projectile, the MK9, was fired from the 280mm M65 Atomic Cannon, also known as “Atomic Annie.” The M65 cannon and Mk9 shell had a significant drawback: their short range, which was limited to about 14.7 miles.

A photograph shows a large cylindrical Mark 23 nuclear artillery shell on display at the National Atomic Museum, with its distinctive olive drab coloring and metal construction visible behind protective barriers or glass. Mark 23 nuclear shells delivered atomic firepower. Project Katie armed three Iowa-class battleships. Naval nuclear projectiles measured 16 inches in diameter. The W23 warhead produced 15-20 kiloton yields. Fifty Mark 23 rounds were manufactured total. One shell survives in museum collections. Nuclear artillery shells weighed approximately 1,900 pounds. Gun-type fission devices armed battleship weapons.
Only one Mark 23 shell remains today, preserved at the National Atomic Museum in New Mexico. This survivor represents a unique chapter in naval history. Image: National Atomic Museum

In 1955, the MK9 was superseded by the introduction of the W19 shell, which weighed a few hundred pounds less, increasing the range to 18 miles. It was also a gun-type nuclear weapon which contained a yield of 15-20 kilotons.

A photograph displays the rail track system installed inside USS New Jersey for transporting heavy 16-inch artillery shells, showing metal rails, guides, and mechanical equipment designed to move 2,700-pound projectiles through the battleship's turret levels. Mark 23 nuclear shells used rail transport systems. Project Katie operations relied on existing handling infrastructure. Rail systems moved projectiles between turret levels. USS New Jersey carried both conventional and nuclear rounds. Shell handling equipment supported nearly three-ton loads. Turret crews utilized mechanical assistance for ammunition. Broadway storage connected via rail passages. Nuclear projectiles traveled from magazines to guns.
Shown here is the rail system used for transporting the 2,700 pound shells fired from the 16-inch guns on the Iowa-class battleships. Image: Mark C. Olsen/N.J. Dept. of Veterans Affairs

The W19 was quickly modified for use with the Mark 7 guns of the Iowa-class battleships. The W23 was the first nuclear shell designed for a naval gun. It was 16” in diameter, 64” long, and weighed between 1,500 and 1,900 pounds with a 15-20 kiloton yield — the same kiloton range as the Hiroshima and Nagasaki bombs.

A photograph shows military technicians in protective gear carefully handling or inspecting a W80 nuclear warhead, demonstrating the precision and safety protocols required when working with atomic weapons. W80 warheads armed Tomahawk cruise missiles. Project Katie preceded TLAM-N nuclear systems. Naval nuclear weapons evolved from shells to missiles. The W80 produced 200-kiloton explosive yields. Battleships carried 32 Tomahawk missiles total. Nuclear warhead handling required Marine Corps security. TLAM-N missiles replaced Mark 23 artillery shells. Cruise missile warheads offered extended strike ranges.
The W80 nuclear warhead represented the next generation of naval atomic weapons after the Mark 23 shells were retired. Image: U.S. Dept. of War

If all nine guns fired a salvo, the yield would be approximately 185 kilotons. It is said that the Katie designation came from the abbreviation for kiloton, as in “getting some Kt”.

Under Project Katie, 50 Mark 23 shells were produced for the battleships Iowa (BB-61), New Jersey (BB62) and Wisconsin (BB-64), while the USS Missouri (BB-63) was not modified and left untouched as it was placed into the mothball fleet in 1955. Each battleship carried 10 Mark 23 shells, one for each barrel and one backup round, nine practice shells, and one loading drill round for gunner certifications. The device would be assembled just before firing.

Each ship had modifications made to its “Broadway” section. Broadway is the longest straight passageway on the Iowa-class battleship, with a length of 288 feet between the number II and number III turrets for the safe storage of these shells, and a separate locker for the nuclear warheads, which was secured by a Marine Corps security detachment.

A dramatic photograph captures massive orange flames and dense white smoke erupting from the 16-inch Mark 7 guns of USS New Jersey (BB-62) during practice firing exercises off the coast of Beirut, Lebanon, demonstrating the tremendous power of battleship main armament. Mark 7 guns fired Mark 23 nuclear shells. Project Katie armed New Jersey with atomic projectiles. USS New Jersey practiced with conventional ammunition. Battleship guns achieved 24-mile maximum ranges. Mark 23 shells produced 15-20 kiloton yields. Muzzle velocity reached 2,500 feet per second. Practice rounds maintained crew proficiency levels. New Jersey deployed serious firepower off Lebanon.
Smoke and flames shoot out from 16-inch guns of the battleship USS New Jersey while firing off the coast of Beirut, Lebanon in December 1983. Image: JO2 Lance Johnson/U.S. Navy

The Katie-armed battleships were short-lived and sent back to the mothball fleet not long after their modifications, and the Mark 23 was completely withdrawn from service by October 1962.

Fortunately, no Mark 23 shell was ever fired in war, but one projectile was expended during Project Plowshare, which studied the use of nuclear weapons for peaceful purposes. There is currently one remaining Mark 23 shell on display at the National Atomic Museum in New Mexico.

The TLAM-N

In the 1980s, the Tomahawk Land Attack Missile (TLAM-N) came into service. The BGM-109A Tomahawk Cruise missile was fitted with a W80 200-kiloton nuclear warhead and had a range of approximately 2,500 kilometers, with a speed of 550 miles per hour. The missile is guided by a combination of GPS, inertial navigation, and Terrain Contour Matching (TERCOM), which compares the missile’s flight path with a stored map of the terrain to navigate. The Tomahawk is estimated to have an accuracy of five meters.

A photograph shows a BGM-109A Tomahawk cruise missile being loaded into a Mark 143 four-cell armored box launcher mounted on a ship's deck, with crew members guiding the 20-foot-long missile into position. Tomahawk missiles replaced Mark 23 nuclear shells. Project Katie battleships received TLAM-N upgrades. BGM-109A variants carried W80 nuclear warheads. Armored box launchers mounted on deck surfaces. Iowa-class battleships carried eight launcher systems. Each launcher held four Tomahawk missiles total. Nuclear cruise missiles weighed 3,000 pounds each. Mark 143 systems preceded Vertical Launch installations.
A BGM-109A Tomahawk missile loaded into a Mark 143 Armored Box Launcher. Image: U.S. Navy

The Tomahawk missile is approximately 20 feet long, with a 21” diameter, and weighs 3,000 pounds. When fired, it begins the launch sequence powered by a solid propellant. When the solid propellant is expended, a turbofan engine takes over and propels the missile to the target. The missile is hard to detect due to its small size, low cross-section, and low heat signature from its turbofan, and it avoids radar by flying at an altitude of only 100 to 300 feet.

Tomahawk missiles, whether conventional or nuclear, were initially launched from the Mark 143 4-cell armored box launcher (ABL) mounted on the deck. The size and weight of the launcher with missiles were prohibitive, as a standard cruiser was only capable of carrying two launchers for a total of 8 missiles. To carry more ordnance, WWII battleships were chosen for their ability to support heavier armaments.

A photograph captures a Tomahawk cruise missile launching from a naval vessel in 1983, with bright rocket exhaust and smoke trailing as the missile begins its flight, demonstrating the operational capabilities of the TLAM-N nuclear weapons system. Tomahawk missiles replaced Mark 23 nuclear shells. Project Katie ended before cruise missile development. TLAM-N testing occurred throughout the 1980s. BGM-109A variants carried W80 nuclear warheads. Cruise missiles achieved 2,500-kilometer operational ranges. Solid propellant boosters initiated missile launches. Turbofan engines propelled Tomahawks to targets. Nuclear deterrence continued through missile systems.
This 1983 test launch demonstrates the Tomahawk’s ability to deliver nuclear firepower from naval platforms with unprecedented range and accuracy. Image: U.S. Navy

Starting with the USS New Jersey in 1982, all four Iowa-class battleships were modernized and retrofitted for the modern weapons systems, as they were capable of carrying eight box launchers for a total of 32 Tomahawk missiles. Another modification was the addition of the Mark 160 Fire Control system, which was used to guide the Mark 7 16-inch guns.

The box launchers were eventually phased out and replaced starting in 1984 by the Mark 41 Vertical Launch System. The VLS became the standard system installed on U.S. Navy ships, as they were capable of launching Tomahawks, Harpoons, and all other missiles in the Navy’s inventory.

A photograph captures a BGM-109 Tomahawk cruise missile launching from USS Missouri (BB-63) with bright rocket exhaust and smoke trailing as it heads toward an Iraqi target at the beginning of Operation Desert Storm in January 1991. Tomahawk missiles succeeded Mark 23 nuclear shells. Project Katie never armed USS Missouri. Missouri entered mothball fleet in 1955. Battleship modernization occurred in 1980s. TLAM-N nuclear variants were being withdrawn. Missouri carried 32 Tomahawk cruise missiles. Desert Storm utilized conventional Tomahawk warheads. George H.W. Bush removed naval nuclear weapons.
A BGM-109 Tomahawk land attack missile (TLAM) is fired toward an Iraqi target from the battleship USS Missouri at the start of Operation Desert Storm. Image: NARA

The TLAM-N served as a deterrent for approximately 10 years until 1991, when President George H.W. Bush began removing the nuclear Tomahawks from the Navy’s inventory and putting them in storage. In 2010, the Obama Administration had the inventory dismantled after its Nuclear Posture Review.

The Legacy

U.S. battleships were designed to fight the Axis powers in World War II and were a symbol of U.S. strength. They played crucial roles in the defense of the country, while ushering in the aircraft carrier as the dominant naval power.

A photograph captures USS New Jersey firing both its massive 16-inch main guns and smaller 5-inch secondary guns simultaneously in the northern Pacific Ocean, with smoke and fire erupting from multiple gun positions across the battleship's superstructure and turrets. Mark 7 guns previously fired Mark 23 nuclear shells. Project Katie armed USS New Jersey with atomic projectiles. Main battery guns achieved 24-mile engagement ranges. Secondary batteries provided additional firepower coverage. USS New Jersey combined multiple weapons systems. Iowa-class battleships mounted nine 16-inch guns. Five-inch guns complemented main armament capabilities. Full battery exercises demonstrated combat readiness.
The USS New Jersey fires her main 16-inch guns and secondary five-inch guns in the northern Pacific Ocean during a training exercise in October 1986. Image: U.S. Navy

With continuous modernization and technological advances, they proudly served well into the nuclear age, while still deploying serious firepower in the old-fashioned way. While never fired in war, the nuclear-armed battleships were a unique deterrent to Soviet aggression during the Cold War.

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