Age and Armor

Battleship armor was not a constant.  It was an ever evolving concept that saw continuous changes in metallurgy, manufacturing, and structural arrangement.  In other words, armor was continuously improving … at least until the post-WWII years at which point it was fairly abruptly abandoned for reasons that remain a mystery (though not for lack of undocumented speculation!).  As such, it is reasonable to expect that the more modern the ship, the better the armor protection.  Given that a ship’s design is locked in at the moment it is laid down, the following list shows the dates that various representative battleships were laid down.  This chronological list suggests that the effectiveness of the ship’s armor scheme was greatest on the latter ships and least effective on the earlier ships.  Thus, the Iowa class would have been the ultimate in battleship armor development both in terms of metallurgy and structural arrangement.  Of course, we’ll never know for sure.
 

 
 

There’s no particular point to this post, just an interesting observation and speculation. 
 

Iowa Class Armor Scheme Cross Section - 
note the internal main belt and incline