An internal citadel for future automated warships

Where would armour provide the most useful protection on a modern frigate?

Around magazines, engineering, command spaces, and connecting passageways, potentially creating a protected crew citadel rather than an armoured outer hull.

Missiles can use several approach profiles, including pop-up attacks, and strike above a traditional armour belt. Protecting the hull still leaves the superstructure, sensors, intakes, and other exposed systems vulnerable. The more practical use of armour is local protection around magazines, engineering spaces, command spaces, and the passageways that connect them. As automation reduces crew numbers, these protected areas could form an internal citadel. Sailors could continue fighting the ship from there after damage. The aim is to preserve combat function rather than attempt to make the entire outer hull invulnerable.