John Fisher, 1st Baron Fisher

Admiral of the Fleet John Arbuthnot Fisher, 1st Baron Fisher, GCB, OM, GCVO (25 January 1841 – 10 July 1920), commonly known as Jacky or Jackie Fisher, was a Royal Navy officer. Fisher was chiefly recognised as an innovator, strategist, and architect of naval reform rather than as an operational admiral, although he held combat commands throughout his career. Appointed First Sea Lord in 1904, Fisher played a critical role in the Anglo-German naval arms race, helping to modernise the British navy ahead of the First World War.

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 of the Navy, 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 HMS Dreadnought, 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.

He first officially retired from the Admiralty in 1910 on his 69th birthday, but became First Sea Lord again in November 1914. He resigned seven months later in frustration over Winston Churchill's Gallipoli campaign, and then served as chairman of the Government's Board of Invention and Research until the end of the war.