The Yan State was developed from a small prince. When the King Yan Zhaowang succeeded to the throne, he sought able people nationwide, collected them at hand and granted outstanding ones important positions. This gradually made Yan a strong state in the north of China.
The Yan State bordered the Qi State on the south, the Zhao State on the west and the Han State on the northeast. On the north the Yan State neighbored small but aggressive minority nationalities mainly Donghu, Linhu and Loufan. They harassed Yan's borders and threatened the security there. To guard against them, in the year 290 B.C., the Yan State built a wall along the Yanshan Mountain Range. The wall started from present Huailai County of Hebei Province, crossed the the Luanhe River, wound on and turned off to the northeast, extended over the Liaohe River and ended in present Liaoyang of Liaoning Province. The whole route ran as long as 1000 li or 500 kilometers. It is the North Wall of the Yan State. It was the last wall built in the Warring States Period.
Yan once succeeded in attacking the Qi State. For fear that the latter would fight back, Yan renovated the embankment of Yishui River and expanded it into a wall. It is known as the Yishui Wall. The Wall consisted of two parts. The first started from present Yixian County of Hebei Province, ran along the Yishui River, passed through Dingxing County and headed to the southeast. The second started from Xushui County of Hebei Province, ran towards the northeast till meeting the first part, then turned off to the southeast and finally arrived at the point about 10 kilometers southeast to Renqiu of Hebei Province.
