In fact, unless forced by adverse circumstances or extreme situations, most generals would not opt to use cavalry in this manner.
For a simple reason: it was too expensive!
The Yan people had always relied on cavalry. Consequently, a major portion of Yan State's annual tax revenue was funneled to the Earl of North Border's command for troop maintenance.
This was why the Jingnan Army maintained both advance and rear camps. It was also why the emperors of Yan, throughout history, had never ventured south. Maintaining an army was already costly enough; if a large-scale war were to erupt, Yan State's treasury simply couldn't support it.
It wasn't that the ancestors of the Yan people were unaware that infantry was cheaper; they simply had no choice. After all, with barbarians as neighbors, they couldn't very well send their men out on foot to fight barbarian cavalry in the desert, could they?
