At its simplest, displacement. A WW2 battleship was only a little less than a modern carrier at around 4-5x the displacement of a destroyer, and around 10x the

At its simplest, displacement. A WW2 battleship was only a little less than a modern carrier at around 4-5x the displacement of a destroyer, and around 10x the displacement of a frigate, with even larger multiples of crew complement. The least manoeuvrable ship of the fleet, typically the flagship of the pre-WW2 battle group with escort of destroyers sometimes also cruisers, frigates and support depending on what it was up to. A role that has been with the carrier in the post-WW2, increasingly missile world. I don't think any navy now retains any battleships, though most kept them around decades past their sell-by date. The battleship (group) was the power that was used to project, and could be sent to far flung locations to bombard an inland target 25 or 30 miles away from the ship, conduct a naval battle or blockade a port well over the horizon. This is the doctrine of the late Victorian era and lapsed in the inter-war years. WW2 and Pearl Harbor very clearly put power projection with the carrier group. The job of the dozen 16" (18" in WW1, and Japanese WW2) and dozen or more 6" guns has been replaced post-war by air, and increasingly cruise and anti-ship missiles in the arsenal. A modern destroyer gets just 1-4 6" pea shooters with range only around 10 miles, but a decent selection of missiles, submarine and air defence that more than makes up for lack of gunnery. Heavy shore bombardment is far cheaper by 16" capital guns than by missile, the last real instance being Desert Storm. In this role a battleship has no peer, it's less accurate than missile whilst flinging an awful lot more weight, but more accurate than heavy bombing. The modern era prefers precision by very expensive munitions. :)