Soldiers assigned to a surface-to-air missile brigade of the air force under the PLA Central Theater Command rush to their positions to erect a surface-to-air missile system during a round-the-clock drill in the hinterland of the Yanshan Mountains in north China on the night of Jan. 21, 2019. The drill aimed to explore the weapon's performance limit under extreme cold conditions and hone the soldiers' night battlefield adaptability. (eng.chinamail.com.cn/photo by Tan Sicheng and He Xiaomin)