The Battle of the Yalu River (黃海海戰, lit. Battle of the Yellow Sea), also called simply 'The Battle of Yalu' took place on September 17, 1894. It involved the Japanese and the Chinese navies, and was the largest naval engagement of the First Sino-Japanese War. The Yalu River is the border between China and Korea, though the battle was actually fought at the mouth of this river,
in the Yellow Sea. A Japanese fleet under Admiral Sukeyuki Ito was attempting to disrupt the landing of Chinese troops protected by a fleet under Admiral Ding Ruchang.
The engagement continued for most of the day, and while it was not the first of pre-dreadnought technology on a wide scale (the Battle of Foochow in 1884 between the French and Chinese predated it), there were significant lessons for naval observers to consider.