Nevada class
    If I had to point to a battleship class which was some kind of a turning point in US battleship design, the Nevada class would be my choice. Profiting from firing-tests, against an old US pre-dreadnought, these vessels began to employ what was to be called the "all or nothing" armor scheme, to become the prime feature of all US battleships.

    The idea was simple. Previous vessels had almost all of their hull armored, not caring whether or not there was something important to protect. The weight that this construction added without considerable gain was lost for heavier armor along vital spaces: ammunition storage, engine and boiler rooms. The new scheme was different. There would be no armor over non-vital areas, but there would be maximum protection for the important places. 

    To accomplish this, the Navy had to alter the mouting of heavy guns from that of the Texas class, with its central turret that would have required seperate armor. Thus, the Nevada returned to the setting of superfiring turrets fore and aft, as it had already been done on the South Carolina class. In order to come out with the same number of 10 x 356mm guns as on the Texas class, while keeping only two ammunition storage areas, one fore, one aft, the Navy introduced a triple 356mm turret. Two of these received the lower positions of the forward and aft turrets, while two twin turrets got placed above them. As a last measure to improve this class over the Texas class, the armor belt was, were it remained, dragged below the waterline, so as to defeat fire that hit the ship below the water. For all their advanced protection, these ships paid with a slower speed, as their new engines, burning exclusively oil, and requiring only half the personal and less weight, made not enough horsepowers to comb with the weight and draft of the ship. 

     Oklahoma, mentioned here first for her shorter wartime history, lay in Pearl Harbor on "the day which will live in infamy", and took her share of the damage in form of four torpedoes, sinking her. Her salvage was highly difficult and only finished in 1944, and since her repair was not; deemed important, and the ship was old anyway, she was sold for scrap in San Francisco, but sank after loosing her tow on the way from Pearl Harbor to San Francisco. 

     Nevada was sunk at Pearl Harbor as well, but was easily salvaged and put into service as a convoy escort for England bound convoys after supporting the Aleutian operations. She shelled the French coast off Normandy, and went into a duel with German coastal batteries at Cherbourg. Then she went to fight against Toulon and Marseille based German coastal defense guns during the invasion of Southern France, before departing for the Pacific were she arrived to shell Iwo Jima and Okinawa with newly emplaced guns, having shot-out her 356mm guns in Europe. She finished her career as target ship for Tests "Able" and "Baker" at Bikini, and survived both, as well as shelling by US battleships and cruisers later. She sank in 1948 after a torpedo from a plane hit her.

(Nevada, 1944):   
10 x 356mm L/45 in two triple turrets and two twin mounts mounted as described   
16 x 127mm L/38 in twin mounts, four on each side   
36 x 40mm L/56   
38 x 20mm
Displacement: 34000 tons   
Length: 177.8 meters   
Beam: 32.9 meters   
Draught: 9.9 meters   
Height (Mast): ????   
Crew: 1301 men   
Speed: 20.5 knots
Complement (Planes)
Three floatplanes
Ships in class: 
BB-36 Nevada 
BB-37 Oklahoma