By February 1938 it appeared increasingly likely that the Second London Treaty’s tonnage related escalator clause will be activated soon due to Japan’s unwillingness to answer questions on its new battleship’s displacement.
If the previous 35kton designs were more in line with the US North Carolina and South Dakota classes than the following ones were more closer to the Iowa and early twelve gun, 45 kton variants of the Montana class.
DNC wanted to see unlimited designs. The two obvious ways to increase the capability of the 35.000 ton variants was to add speed or firepower while restoring the full 16 gun secondary battery and a cross-deck catapult with two adjoining hangars, all at the same time.
16D-38 added length for an increased machinery with a maximum output of 150.000 SHP, calculated to be enough for 30-31 knots. These were somewhat optimistic figures given the power allotment but through the introduction of a longer hull and a transom stern (which virtually increased length even further) it was not out of reach.
They had an immunity zone of 14.000-30.000 yards versus their own 16″ shells. Still a much improved splinter protection scheme had been included in these designs, together with a TDS that could resist up to 1000 pounds (445kg) warheads.
16E-38 approached from a firepower point of view, with adding a 4th triple turret aft in a superfiring position between the aft superstructure and turret. It retained the KGV class machinery with a resulting speed of only 26-27 knots. Protection (including splinter armor and TDS) duplicated 16D.
The increased main battery really elevated this variant above the others but armor remained the same and speed fell below previous standards, so this wasn’t a balanced design at all. It’s appearance is also a bit deceiving, in reality this design stood much closer to the US Iowa class than to the Montanas as finally approved.
Neither of the above designs were submitted for the 3rd Sea Lord (Controller) for further development as in the meantime negotiations were still going on about the exact new, escalated tonnage limit. Also a new set of staff requirements had been issued in the meantime that placed focus on some secondary characteristics.