John Arbuthnot Fisher was a British admiral known for his significant influence on the Royal Navy during the late 19th and early 20th centuries. He served as First Sea Lord, the professional head of the British naval service, and was a key figure in modernizing the navy and advocating for technological advancements. Fisher was also known for his controversial and forceful personality, as well as his strategic thinking and innovative ideas. He played a crucial role in shaping the Royal Navy into a modern and powerful force.