Fisher saw the need to improve the range, accuracy and rate-of-fire of naval gunnery, and became an early proponent of the use of the torpedo, which he believed would supersede big guns for use against ships. As Controller, he introduced torpedo-boat destroyers as a class of ship intended for defence against attack from torpedo boats or from submarines. As First Sea Lord he drove the construction of , the first all-big-gun battleship, but he also believed that submarines would become increasingly important and urged their development. He became involved with the introduction of turbine engines to replace reciprocating engines, and with the introduction of oil fuelling to replace coal. He introduced daily baked bread on board ships, whereas when he entered the service it was customary to eat hard biscuits, frequently infested by biscuit beetles.