The Tillman No.4 series

The Tillman Battleships

In July 1912, a resolution introduced in Congress by Senator Benjamin Tillman (D-SC) of the Senate Naval Affairs Committee directed the Navy to explore the maximum practical limits of battleship design. Battleship size had been increasing incrementally, and the latest generation of battleships was now approaching 30,000 tons. Over the next few years the Bureau of Construction and Repair turned out numerous designs; each, at Tillman’s prodding, larger, faster and more heavily armed than the previous.

Some of these designs evolved into what later became the Pennsylvania, New Mexico, Tennessee and Colorado classes, but these never approached what Tillman felt were the ultimate limits of size, speed, gun power and protection. In 1916 he succeeded in securing four preliminary designs from C&R that were derived from the still evolving 43,200 ton South Dakota class. Though each varied in armament, protection, horsepower and speed, all were designed to the maximum limits permitted by existing harbor and docking facilities at the time, and dimensions were specifically tailored to fit the locks of the Panama Canal. Each design called for ships that were 975ft x 108ft x 32ft-9in, with a radius of action set at 12,000nm at 10kts. Individual design schemes varied as follows:

 Design 1 retained the same armament of the South Dakotas (12-16in/50 in 4 triple turrets) on a displacement set at 70,000 tons. This allowed the armor thickness to be increased and the speed to be raised to 26.5kts at 65,000SHP.
 Design 2 kept the same displacement and speed as Design 1, but doubled the main armament to 24-16in/50 in 4 sextuple turrets. To compensate for this,armor thickness was reduced to South Dakota’s level.
 Design 3 retained the armament and protection of South Dakota, but raised the speed to 30kts. This required an increase in SHP to 90,000, yielding a displacement of 63,500 tons.
 Design 4 combined the increased protection of Design 1, the armament of Design 2 and the horsepower of Design 3 for a displacement of 80,000 tons and a speed of 25.2kts.

In January 1917, Design 4 was further modified by substitution of 18in guns for 16in on the same 80,000 ton displacement. To maintain the same 25.2kt speed, a sacrifice in protection was required that reduced the maximum thickness of the belt armor from 18in to 16in. Re-designated Design IV, this called for two alternate dispositions of the main armament:
 Design IV-1: 15-18in/50 in AB-PQ-XY positions with dual mounts super-firing over triple mounts.
 Design IV-2: 15-18in/50 in AB-XYZ positions, all triple mounts.

In conclusion, these design studies served a useful purpose in showing what form a maximum build out at this time might have assumed. These monsters, however, at the stage to which their design was taken, embodied no breakthroughs in design or construction such as sloped armor or enhanced internal subdivision. Their protection relied on the old pre-WWI belt/protective deck system, and their underwater cross-section is essentially the same multilayer internal subdivision system as was designed for the Colorado class.

Further design work might have seen this radically modified as the lessons of Jutland and the potential for air attack were taken into account, and these ships might have emerged, at astronomical cost, as a new defining type.

As an operational rule, Navy Secretary Josephus Daniels favored classes of six, with five operating as a division so that one could be kept under repair at any given time.