Napoleon ruled as Emperor of the French for 10 years before his first abdication. The French Senate proclaimed him emperor on 18 May 1804, and he was crowned at Notre-Dame de Paris on 2 December that year. He signed his first abdication on 6 April 1814 after Allied armies invaded France and Paris fell.
The ten-year figure is a rounded calendar-year count: from 1804 to 1814, Napoleon’s imperial rule lasted just under a full decade from proclamation to abdication. Some accounts emphasize the 2 December coronation, while others use the 18 May constitutional appointment, but both dates lead to the same quiz answer.
Napoleon did not disappear from power permanently. He was exiled to Elba, returned to France in March 1815, and ruled again during the Hundred Days. His second and final abdication followed defeat at Waterloo in June 1815.