Medieval armour as a capital-ship design analogy

Full plate, a large shield, and heavy weapons stand in for the conventional battleship: well protected and powerful, but slow and tiring to move. The fast battleship gives up some armour coverage for mobility while retaining a breastplate, helmet, shield, and a weapon with reach. The one-word battlecruiser keeps enough protection to survive a dangerous encounter and relies more heavily on speed. The original dreadnought armoured cruiser, or two-word battle cruiser, sits farther toward the mobile end, with limited armour and a useful weapon but little chance in a sustained fight with a fully protected opponent. The analogy explains how these categories differ by degrees of protection, subdivision, and purpose rather than by a single specification.