Zhongshan 中山 was a regional state of the Zhou period 周 (11th. cent.-221 BC). It was not one of the Chinese states of the ancient system of regional states of the Zhou dynasty but a native, semi-"barbarian" state in the mountain area between the modern provinces of Hebei and Shanxi.
Map according to Tan Qixiang 谭其骧 (1987), Zhongguo lishi ditu ji 中国历史地图集. The semi-barbarious state of Zhongshan was located in central Hebei and did not play a decisive political role. It was conquered by its western neighbour Zhao. Click to enlarge.
It was founded by a chieftain of the White Di 白狄 tribes during the Spring and Autumn period 春秋 (770-5th cent. BCE) under the name of Xianyu 鮮虞. Their territory was often involved in conflicts with the state of Jin 晉. The name Zhongshan is first mentioned in the chronicle Zuozhuan 左傳 for the year 506. This state covered the region of the modern districts of Lingshou 靈壽, Pingshan 平山, and Jinxian 晉縣, Hebei.
Historiographical documents about the state of Zhongshan are very rare, most are to be found in the books Zhanguoce 戰國策 and Lüshi chuqiu 呂氏春秋. The Qing period 清 (1644-1911) scholar Wang Xianqian 王先謙 (1842-1918) published a collection of such data, the Xianyu Zhongshan guo shi biao 鮮虞中山國事表. In 1971, the tomb of a king of Zhongshan was unearthed, and many bronze tools with inscriptions were discovered. The inscriptions included also historiographical material.
In 414, King Wu of Zhongshan 中山武王 was enthroned. His capital was located in Gu 顧 (modern Jinxian, Hebei). In 408 ,the kingdom of Zhongshan was destroyed by Wei 魏， but was able to recover. It is believed that the second state of Zhongshan was actually a foundation by a lateral branch of the house of Wei, but the inscriptions on the unearthed bronze tools prove that the rulers of the second state of Zhongshan were indeed descendants of late King Wu. During the Warring States period 戰國 (5th cent.-221 BCE), Zhongshan was a relatively strong state. The king of Zhongshan was even officially made a regional ruler (zhuhou 諸侯) by the king of Zhou, first as a marquis (hou 侯), and from 323 on as king (wang 王), in the same year when the rulers of Han 韓, and Yan 燕 adopted the title of king.
Zhongshan was allied with the state of Qi 齊 in the east and threatened the eastern border of Zhao 趙, where the king of Zhongshan erected a fortification wall. In 314, the king of Zhongshan participated in Qi's campaign against the state of Yan in the north and occupied large tracts of land in Yan. From 307 on, King Wuling of Zhao 趙武靈王 (r. 326-299) almost annually attacked the state of Zhongshan and weakened its forces, to that in 301, the king of Zhongshan was forced to take refuge in Qi. When the king of Qi undertook a campaign against the state of Chu 楚 in the south, King Huiwen of Zhao 趙惠文王 (r. 299-266) saw his chance to conquer the territory of Zhongshan. This happened in 295.