King Wuling of Zhao 趙武靈王 (r. 326-299, d. 295 BCE), personal name Zhao Yong 趙雍, was a ruler in the state of Zhao 趙 during the Warring States period 戰國 (5th cent.-221 BCE). He is famous for his military reform.
The reform was motivated by the permanent raids of northern tribes of the Hu people 胡 who used cavalry while the states of the Zhou empire still relied on chariots and armoured infantry. In order to fight the mounted archers of the Hu, King Wuling ordered in 307 to imitate their fighting style, equipped his riders with short jackets and trousers, leather belts and leather shoes, and had them learn mounted archery. The King's decision met resistance at the court, mainly by the princes Gongzi Cheng 公子成, Zhao Wen 趙文, Zhao Zao 趙造, Zhao Jun 趙俊, and minister Zhou Shao 周紹. Yet he was able to convince them, and thus created China's oldest genuine cavalry units (see Zhou military), the "mounted archers with barbarian clothes" (Hufu qishe 胡服騎射). In 302, he even ordered his courtiers to wear short-style clothes.
King Wuling's idea was that "ruling the world was not depended of one single path, and the governance of a state laid not in imitating the past" (li shi bu bi yi dao, bian guo bu bi fa gu 理世不必一道，便國不必法古).
With his novel forces, King Wuling annihilated the state of Zhongshan 中山 (region of Lingshou 靈壽 and Tangxian 唐縣, Hebei), and defeated the wild tribes of the Linhu 林胡 and Loufan 樓煩 at the northwestern borders of Zhao, where he established the commanderies of Yunzhong 雲中 and Yanmen 雁門 and ordered to build a wall against the wild tribes.
In 299, he decided to retire and hand over the throne to his son Prince He 何, who is known as King Huiwen 趙惠文王 (r. 299-266). King Wuling himself adopted the title of King Father (Zhufu 主父) and chose Shaqiu 沙丘 (Pingxiang 平鄉, Hebei) as his residence. In 295, Prince Gongzi Zhang 公子章, Lord of Anyang 安陽君, rose in rebellion, and, defated, fled to Shaqiu, where he found protetion by the King Father. The royal abode was besieged by Li Dui 李兌, who loyally served King Huiwen. He beleaguered the rebel so long until he could kill the rebel and the King Father died of starvation.