MC - Bought land in a mountain near his school His father is in the imperial court Borrowed a command medallion form a general. Has a battle defending a mountain pass He made the pass using his knowledge of making concrete One of their enemies could only eat meat and not rice The Mc army was dehydrated but he dug a spring in the mountain shocking their enemies. Novel either Chinese or Japanese novel.
Huuuuuh i don't think it's japanese. Unless it's not a not popular or not one with a lot of chapters.
Human emperor Mountain and water and concrete works. Father is general but has uncle in court. Enemy food is based on herding animals not agriculture.