Zhao Yun set up cauldrons and lit fires before the lines. Zhang He had watchtowers in his camp, and the firelight immediately drew the scouts' attention. Zhang He soon learned of the Han Army's new "move," but made no corresponding deployment, merely ordering the scouts atop the towers to continue watching.
An hour later, the fragrance of food drifted from dozens of cauldrons, carried by the valley wind toward the Wei Army camp.
In order to have sunlight for warmth each day, Zhang He had deliberately pitched camp facing south, backed by high mountains and beside water, leaving the shadowed northern side for Zhao Yun and Huang Zhong.
Camping on the sunny side let them absorb the sun's warmth. It was practically a reenactment of the layout at Dingjun Mountain, forcing the Han Army to attack from the shaded side while Zhang He claimed every advantage of terrain and climate. After choosing the campsite, Zhang He had smugly congratulated himself for days—only for Zhao Yun to slap him across the face.
The southward-blowing wind through the valley passed through the Wei Army's encampment before being blocked by the high mountains to the north. Part of it then formed a backflow, eventually dissipating within the Wei camp.
Cold wind alone would not have mattered much. The Han Army camp could not escape the cold either, and for most of the day it received no sunlight. But the fatal thing was that Zhao Yun had employed a war of scents. The pots held kelp, dried fish, radishes, and other ingredients. The aroma lingered in the valley for a long time, and whenever a north wind passed through, it carried the scent into the Wei camp.
The Wei Army's two daily meals only ever left them half-full, yet it was not even noon