Original title (ZH): 得闲谨制 (Déxián jǐn zhì, Exercise caution when you have free time)

A group of Chinese refugees and straggler soldiers, led by a machinist, defend their mountain town, “Gezhi,” against a surprise attack by Japanese reconnaissance troops in a desperate fight using civilian ingenuity against a trained military force.

https://www.themoviedb.org/movie/1356454