Conning towers

In the late 19th Century, battleship and armored cruiser design always included an armored conning tower. By the late 1930's, the British had eliminated this feature. Instead, they contented themselves with moderate armor on the conning station, in the bridgework. Admittedly, on the Hood and Nelson class, they had gone overboard with conning tower design. In typical government bureaucratic fashion, they overspecified what was needed, and so they got the $1000 toilet seat of conning towers. Reportedly, when the Hood exploded and sank, the conning tower fell out, as the ship capsized. The weight was over 200 t0ns. After the fact, the Americans discovered that having a strong conning tower was a good thing. In the battle against the Japanese battlecruiser Kirishima, the battleship South Dakota was hit on the bridgework, and many exposed crewmembers were killed or wounded. The captain was conning the ship from the conning tower, and he and the ship survived the battle. After the battle, the Americans abandoned the move towards eliminating the conning tower. Admittedly, the West Virginia, California, and Tennessee had their heavy, battleship conning towers removed and replaced with cruiser conning towers.