sentences:  These shells were designed to be launched from the best seaborne artillery platform available, which at the time were the four ships of the "Iowa" class.The shells entered development around 1953, and were reportedly ready by 1956; it is not known whether they were ever deployed on the "Iowa"-class battleships because the US Navy does not confirm or deny the presence of nuclear weapons aboard its ships.In 1991 the US unilaterally withdrew its nuclear artillery shells from service, and Russia responded in kind in 1992.