A two-calibre treaty forces every navy into awkward compromises

Which two gun calibres should each navy retain if a treaty allowed only two weapons above 58 mm?

Britain would probably combine an intermediate rapid-firing gun with 16-inch battleship weapons, while the United States would likely choose 8-inch and 16-inch guns.

Few navies would accept so restrictive an arms-control rule. If forced to choose, Britain would need a rapid-firing intermediate gun able to cover destroyer and cruiser work, paired with a heavy capital-ship calibre. A 5.5-inch and 15-inch combination is possible, but roughly 4.8-inch and 16-inch guns better fit the new Nelson and Rodney. That choice could pull the later King George V class toward a Lion-like 16-inch armament, while the United States would likely prioritize 8-inch and 16-inch guns for its own force structure.