The famed Iowa-class battleship, known for its imposing firepower, was almost upgraded to feature more firepower, indeed, the most firepower. During the 1950s, while the Cold War raged, the U.S. Navy considered Iowa-class modifications that would have allowed for the firing of nuclear artillery shells. It’s true. The Iowa was almost converted into a nuclear-weapon deploying vessel.  

Upgrading the Iowa 

During the Cold War, the U.S. developed and adhered to a nuclear deterrence strategy that was dependent upon a nuclear triad. The nuclear triad comprised methods for deploying nuclear weapons from air, land, and sea. 

The Air component consisted of nuclear weapons dropped from strategic bombers like the B-52. The land component consisted of intercontinental ballistic missiles, like the Minuteman, fired from subterranean silos in the United States. The sea component consisted of nuclear missiles launched from submarines, like the Ohio-class. But the sea component was almost augmented to include nuclear artillery shells from the Iowa-class. The artillery shells were known as the Mk 23 (W23) “Katie.” 

Meet Katie 

The Katie was developed from the Mk 9, which was the world’s first artillery-fired atomic projectile, or AFAP. Developing an AFAP was far from simple. “An artillery shell is an incredibly difficult environment to put a complicated device like a nuclear warhead,” NavalGazing.net reported. “It must withstand normal handling, thousands of G’s of acceleration as it’s fired, and the centrifuge of a shell spinning at 10,000 rpm or more…And it needs to be compact.” 

The eventual solution was the Katie, which was a variant of the W19, which in turn was a derivative of the Mk 9. The W19 was an AFAP with a 15-20 kiloton yield; the W19 measured eleven inches in diameter, fifty-four inches long, and weighed 600 pounds. 

The Katie, meanwhile, was sixteen inches in diameter, sixty-four inches long, and weighed between 1,500 and 1,900 pounds. So while the Katie was bigger than the W19, the kiloton yield was the same, at fifteen to twenty kilotons. For the sake of comparison, consider that the Katie’s kiloton yield is roughly comparable to the atomic bomb dropped on Hiroshima, which killed between 90,000 and 166,000 people.   

Only fifty Katies were ever produced, beginning in 1956. The Katie only remained in service until 1962.  

Nuclear-Armed Ships? 

The Pentagon ultimately abandoned the Katie project, which was quite expensive. Whether the Iowa ever carried any Katie shells remains unknown, consistent with a U.S. Navy policy of neither confirming nor denying the presence of nuclear weapons aboard its vessels.  

The U.S. stockpile has all reportedly been dismantled, however. The United States is understood to have unilaterally withdrawn all of their AFAPs from service in 1991, after the Soviet Union collapsed, and is understood to have dismantled their last AFAP by 2003.  

Harrison Kass is a defense and national security writer with over 1,000 total pieces on issues involving global affairs. An attorney, pilot, guitarist, and minor pro hockey player, Harrison joined the US Air Force as a Pilot Trainee but was medically discharged. Harrison holds a BA from Lake Forest College, a JD from the University of Oregon, and an MA from New York University. Harrison listens to Dokken.      

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