Can a fast battleship keep battleship protection?

Can higher-power machinery make a battleship fast without sacrificing survivability?

Greater machinery power density makes high speed and strong protection compatible, but the added cost and complexity still need a useful operational role.

More compact power plants can reduce the penalty of fitting enough machinery for high speed. Improved structure and armour arrangements also change the design tradeoff. Where battlecruisers already perform the fast role, the question is whether a more expensive fast battleship adds enough value. A heavily protected ship intended to defeat other fast capital ships could emerge under either battleship or battlecruiser terminology. A possible postwar response to continued Soviet battleship construction remains counterfactual.