行军 (xíngjūn) means "to march" or "a march," referring to soldiers or troops traveling on foot in formation. It is used in military contexts to describe the movement of an army from one place to another.
士兵们在雨中行军了一整天。
Shìbīngmen zài yǔ zhōng xíngjūnle yī zhěng tiān.
The soldiers marched in the rain for an entire day.
这次行军的距离超过了五十公里。
Zhè cì xíngjūn de jùlí chāoguòle wǔshí gōnglǐ.
The distance of this march exceeded fifty kilometers.
部队天没亮就开始行军了。
Bùduì tiān méi liàng jiù kāishǐ xíngjūn le.
The troops began marching before dawn.