thus, the maximum thickness of armor would be around the magazine area, leading to the final manifestation of the ‘all or nothing’ scheme. In practice No navy built pure "all or nothing" battleships although most navies put the theory into use to some degree. Even Japan's giant was armored along all-or-nothing principles as there simply was no other way to provide the heroic scale of protection they required. Of the battleships designed and built within the full constraints of the Washington Treaty, the Royal Navy's Nelson class and the French Navy's Dunkerque class came closest to the ideal. Even in these ships some degree of "splinter protection" was included to protect key systems and personnel from fragmentation damage. From the on to its Iowa class 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. The misgivings of building a pure "all or nothing" ship were that they had areas still vulnerable to guns of even modest warships, small arms fire, blast damage from a ship's own guns, bombs, strafing, and torpedoes. For instance, blast damage was to plague the careers of the Nelson-class ships, a situation aggravated by the positioning of their guns. The superstructure, for instance, housed crucial command stations, communications, and radar equipment. Regardless of armoring scheme used, many critical areas such as the rudder, propellers, and bow could not be protected, so damage to these areas could reduce a ship's maneuverability and buoyancy.