Battlecruiser armour, speed, and strategic tradeoffs

An armour analogy distinguishes a dreadnought armoured cruiser, a more developed battlecruiser, a fast battleship, and a fully protected battleship by the extent of their coverage. Greater protection costs weight, and the balance remains a design problem even without naval treaties or dockyard limits. A battlecruiser's sustained cruising speed is especially useful: an advantage of four or five knots can shorten a strategic redeployment. That lets the ship reach a distant concentration or chosen target sooner. Accepting less protection is therefore a decision about the jobs the ship must perform and the risks those jobs justify. The closing lance-and-shield comparison expresses that strategic distinction, with the battlecruiser valued for reaching and striking a target.