Battleship armour was not intended to make a ship invulnerable to heavy shells at every range and angle. A protection scheme instead created a zone in which inclined or horizontal armour had a reasonable chance of defeating the expected trajectory. Even successful armour could be cracked, displaced, or weakened by the first hit in an area, allowing a later shell to penetrate nearby. That cumulative damage helps explain why admirals valued rate of fire as well as single-shot accuracy and penetration.
Notable Point · 13:39-17:34
Why battleship armour only works within limits
Warspite's protection introduces the relationship between shell angle, fighting range, repeated hits, and battleship rate of fire.