A submarine attached to a naval submarine flotilla under the PLA Northern Theater Command steams in the sea during a training exercise on March 21, 2023. (eng.chinamil.com.cn/Photo by Wu Haodong)

A submarine attached to a naval submarine flotilla under the PLA Northern Theater Command bears off a port after separating from the towboats during a training exercise on March 21, 2023. (eng.chinamil.com.cn/Photo by Wu Haodong)

Two towboats attached to a naval submarine flotilla under the PLA Northern Theater Command tow a submarine to bear off a port during a training exercise on March 21, 2023. (eng.chinamil.com.cn/Photo by Wu Haodong)