Operation Katie was the program. Battleships were to use Army tactical nuclear shells.

Several attempts to unretire the remaining U.S. Navy or Iowa-class battleships have succeeded. Could those battleships carry and discharge nuclear ordinance? Yes.

The U.S. Navy had its demands and rivalries with other services during the Korean War in the early 1950s. The Army, Air Force, and Navy submarines had nuclear weapons, but surface ships could not. Then they made three Iowa-class battleships so their main 16-inch guns could fire atomic shells.

Operation Katie was the program. The name derives from kilotons (kt). Battleships were to use Army tactical nuclear shells. Fifty Mark 23 “Katie” nuclear projectiles were created in 1952 and arrived in 1956.

The Navy added magazines to hold shells to the USS Iowa, USS New Jersey, and USS Wisconsin, 10 Katie projectiles, and nine practice shells per ship. It would provide the Navy with the world’s most powerful nuclear cannon at 135–180 kilotons.

The Army’s Mark 9—the first nuclear artillery shell—inspired the Mark 23. The Navy’s Mark 23 had a 15-20 kiloton nuclear payload, similar to the bombs detonated on Hiroshima and Nagasaki to end WWII. As a result, Katie can destroy a city at any time of day or night, in any weather. It might eradicate a Soviet battle group at sea. Navy nuclear shells were accurate.

Shells needed meticulous engineering. Navy Gazing, a blog on the USS Iowa and other battleships, said this regarding nuclear artillery.

“A nuclear weapon in an artillery projectile is really tough.” “It must endure typical handling, hundreds of gs of acceleration when discharged, and the centrifuge of a shell spinning at 10,000 rpm or more.”

As expected, the Navy never confirmed or denied that the ships had nuclear shells.

Battleships may have used the shells. Nuclear planners thought the U.S. could “win” a nuclear war with the USSR. The Katie shells indicated the military’s nuclear ambitions. Conventional combat could escalate to nuclear war.

Fred Kaplan wrote about how the military thinks in his book The Bomb: Presidents, Generals, and the Hidden History of Nuclear War.

“All of these possibilities see the bomb as a massive war weapon. From the start of the nuclear era to the present, the U.S. military’s doctrines, drills, and exercises have reflected this perspective.

Katie was part of a military strategy that retrieved the shells after a 1957 practice round on the Battleship Wisconsin. Today, Albuquerque’s nuclear museum displays a Mark 23 shell.