The guided-missile frigate Zhangjiakou (Hull 605) attached to a frigate flotilla with the navy under the PLA Northern Theater Command fires its main-gun against mock sea targets during a maritime training exercise in waters of the Yellow Sea in mid December, 2020. (eng.chinamil.com.cn/Photo by Wang Guangjie)

A ship-borne Z-9 helicopter attached to a frigate flotilla with the navy under the PLA Northern Theater Command prepares to land on the flight deck of the guided-missile frigate Zhangjiakou (Hull 605) during a maritime training exercise in waters of the Yellow Sea in mid December, 2020. (eng.chinamil.com.cn/Photo by Wang Guangjie)

A ship-borne Z-9 helicopter attached to a frigate flotilla with the navy under the PLA Northern Theater Command prepares to land on the flight deck of the guided-missile frigate Zhangjiakou (Hull 605) during a maritime training exercise in waters of the Yellow Sea in mid December, 2020. (eng.chinamil.com.cn/Photo by Wang Guangjie)