His strategic goal was very clear, which was to go south at any cost.
Invade south, attack south, sweep south, retreat south, gather as many people as possible, seize resources, take all the belongings that could be carried, and then with a single push, cross the Gen River, head to the Central Plains, and avoid the edge of the demon's blade.
Yes, after all, they were people who came out of the freezing lands like Kan State, who wouldn't know the power and insolubility of the demonic threat.
Hebei simply couldn't be defended; no matter how strong the Mystic Sect was, how long could they hold back the Demon Tide? Once the patience of the Immortals was exhausted, who could mend the heavens with a single hand and save the world?
The worst-case scenario is, perhaps this winter, a new batch of Demon Tides hatch successfully, and millions of beast hordes would probably trample over the Nine Borders, heading south.