Admiral of the Fleet John Arbuthnot "Jacky" (or "Jackie") Fisher, 1st Baron Fisher, (25 January 1841 – 10 July 1920) was a British admiral known for his efforts at naval reform. He had a huge influence on the Royal Navy in a career spanning more than 60 years, starting in a navy of wooden sailing ships armed with muzzle-loading cannon and ending in one of steel-hulled battlecruisers, submarines and the first aircraft carriers. The argumentative, energetic, reform-minded Fisher is often considered the second most important figure in British naval history, after Lord Nelson.