John Fisher secured approval from Churchill for Renown and Repulse by promising to use material already available and repeat the rapid construction achieved with Dreadnought. Although based on battleship designs, high speed alone did not make them fast battleships. Both types needed speed and range, so classification depended on purpose and intended employment. A fast battleship used speed to enter or sustain battle; a battlecruiser used it to control or avoid battle.
Chapter · 21:36-23:45
Renown, Repulse, and classification by purpose
Fisher's wartime bargain for Renown and Repulse leads into the mission-based distinction between a fast ship meant to fight a fleet battle and one meant to control whether battle occurs.