Spear in Hand, Gazing North: I Am Yuan Xi

A modern person, preferably a history student, civil servant, or project manager with knowledge of organization, management, and historical trends rather than a pure tech nerd, transmigrates into Yuan Xi on the eve of the Battle of Guandu, around 199–200 AD. The original Yuan Xi has fallen from his horse and been injured, or has fallen unconscious from a sudden illness, giving the protagonist an opportunity to take over.