The Blockade of Wonsan, or the Siege of Wonsan, from February 16, 1951 to July 27, 1953, during the Korean War, was the longest naval blockade in modern history, lasting 861 days. UN naval forces, primarily from the United States, successfully kept the strategically important city of Wonsan from being used by the North Korean Navy. The blockade also served to divert communist troops from the front line. North Korean resistance used artillery to oppose the American fleet, although this was mostly ineffective, and the city was heavily damaged by UN naval aircraft and warships.