The Southern Border, which has been under the management of the Imperial Jiang Family for many years, can be considered the base for a desperate counterattack. Due to its unique topography, this place is desolate and uninhabited, making it impossible for the Imperial Astronomer to intervene, let alone find a foothold.
There isn't a crack to exploit.
With cards on the table, King Yan sees the Southern Border as a major threat and has stationed heavy troops on the southern front.
However, he is acutely aware that loyalties to the royal state aren't confined to the Southern Border. If he rashly mobilizes soldiers and concentrates the Imperial Astronomer's power on the Southern front, chaos will inevitably ensue in the secure rear flank.
As a capable commander, King Yan, who controls the whole territory of Zhaoqin, gives an external solution.