From the on to its , the United States Navy pioneered the all or nothing approach without taking it to its logical conclusion. For example, the US designed its battleships to give the crew additional protection instead of relying only on the armored deck of the citadel. These vessels had three armored decks: a sacrificial armored top deck to decap and set off bombs and shells; a splinter deck between the top and citadel decks to protect the majority of the crew from shell and bomb fragments; and a heavy armor citadel deck protecting the machinery and magazines. On the "Iowa"-class ships, the splinter deck is below the citadel deck. In World War II-era fast battleships and modernized Standard-type battleships, the secondary armament was also in armored turrets, the same type of mounts also found in newer fleet carriers and cruisers, since this was a vital defense against enemy aircraft (particularly Kamikazes). The US could also afford to construct large portions of their battleships using Special Treatment Steel (STS), a ductile armor which provided both structure and splinter protection.