Fisher's speed doctrine and the limits of Renown

Fisher's claim that speed could substitute for armor had real force when a few knots represented a large proportional advantage. His work on torpedo boat destroyers, including the Daring class, gave the speed argument a practical small-ship application. As Third Sea Lord he also balanced new ideas with conventional fleet needs more readily than he later did as First Sea Lord. HMS Renown nevertheless shows the risk of buying speed with protection and firepower: her 19 knots briefly outpaced the Majestic class, but the Canopus and Formidable classes rapidly narrowed the gap while carrying heavier guns. Improving machinery could therefore erase a speed advantage within a few years while the original sacrifices in armor and armament remained built into the ship.