Admiral of the Fleet John Arbuthnot Fisher, 1st Baron Fisher,, 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.