Why an eight-inch gun does not define a useful heavy cruiser

Treaties called an eight-inch-gunned ship a heavy cruiser, but that legal category did not define the ship's actual fighting role. Before radar, six- and eight-inch guns could have very similar effective engagement ranges, while a six-inch cruiser offered useful volume and flexibility across more missions. Many treaty heavy cruisers were better understood as scouts carrying a legally defining gun caliber. The comparison explains why the Royal Navy could regard six-inch cruisers as more useful despite the apparent advantage of larger shells.