Queen Elizabeth raises the calibre stakes

Britain's move from 13.5-inch to 15-inch guns appears here as a response to other navies adopting 14-inch weapons, especially the United States. The increase was larger than Britain needed merely to overmatch contemporary German guns. The familiar 1.5-inch increments were a practical logistical pattern rather than an inflexible rule. When foreign designers later considered 16-inch weapons, British planning could look past a hypothetical 16.5-inch step toward 18-inch battleship guns. A 16-inch option for a battlecruiser would preserve the speed that type required, keeping calibre tied to role and machinery.