In April 1951, Chinese Navy organizes a group to learn submarine knowledge from the Pacific Fleet of former Soviet navy in Lushun, Dalian, northeast China's Liaoning province. In May 1952, China founds its first submarine base in Qingdao, east China's Shandong province. In June 1954, China establishes its first submarine force to conduct patrol and vigilance missions. (File photo/ Navy.81.cn)