This stalemate lasted until dusk, when a sandstorm obscured the battlefield. Wei Qing used the tactical advantage of the confusion surrounding the sandstorm to send in his main force. The Han cavalry used the low visibility as cover and encircled Chanyu's army from both flanks. The Xiongnu's lines were overwhelmed, and their morale broken by the sight of Han soldiers attacking them in the darkness. Seeing that his forces were completely overrun, the Chanyu escaped under the escort of only a few hundred men. The Han forces killed over 19,000 enemies and pursued the remainder another 100 miles to the Khangai Mountains where they besieged then captured the Fortress of Zhao Xin located in the Orkhon Valley. After a day spent regrouping and receiving fresh supplies, the Han forces burned the stronghold to the ground, before returning in triumph.