The battle arose from an attempt by part of the Chinese Nanyang Fleet (Southern Seas fleet) to relieve the French blockade of Formosa (Taiwan). On 18 January 1885 the Chinese cruisers Nanchen (南琛), Nanrui (南瑞) and Kaiji (開濟) left Shanghai, accompanied by the frigate Yuyuan (馭遠) and the composite sloop Chengqing (澄慶), and sailed towards Formosa. The Chinese flotilla was under the command of Admiral Wu Ankang (吳安康). The Nanyang ships were originally to have been accompanied by Chaoyong (超勇) and Yangwei (揚威), two relatively modern cruisers from the Beiyang Fleet, under the command of the German 'guest-admiral' Siebelin, but Li Hongzhang diverted these two Beiyang ships to Korean waters. (Tension between China and Japan over Korea was running high at the period, following Yuan Shihkai's defeat