 The Japanese Navy, after the capture of Canton (Guangzhou) the previous year, had maintained a formidable blockade all along the coast of south, central and north China.However, loopholes were found in the southern end of the blockade line.These included the supply route to Chiang Kai-shek with Hong Kong and Northern French Indo-China as relay points and the direct routes through Hainan Island and Kwangchowan areas.