As the lord of the Northern Frontier, Yanyan had to consider the soldiers and people under his command; he could never agree to the alliance request of the combined forces.
Once he led his troops southward, the Xiongnu and the Donghu, who urgently needed to recover their strength, would never miss this opportunity to encroach upon Loufan, Yunzhong, and Jiuyuan.
The reason he would ally with the Qin army was that Qin's demands aligned perfectly with what he was already doing!
Chapter 223