The Nitro-class ammunition ships are a class of three auxiliary vessels of the United States Navy. Launched in 1958-1959, they were among the first specialized underway replenishment ships built after the Second World War, to carry munitions. These and the Suribachi-class ammunition ships are sometimes considered to form a single class. A fourth ship of the class was planned under the 1959 military construction program but was eventually cancelled before construction began. Soon after completion, all ships of the class were modified to stow surface to air missiles as large as the RIM-8 Talos in their holds. Initially ships of the Nitro class were armed with eight 3"/50 caliber guns in Mk 33 twin mounts. Two Mk 33 mounts were located on the forecastle and another two were located near the s