Photo taken on May 4, 2019 shows the naval forces paticipating in the "Joint Sea-2019" exercise. A six-day joint naval exercise held by Chinese and Russian navies concluded Saturday in Qingdao, east China's Shandong Province. Two submarines, 13 surface ships, as well as fixed-wing airplanes, helicopters and marines participated in the exercise. (Xinhua/Li Ziheng)