Emperor Han Wudi 漢武帝 (156-87, r. 141-87 BCE), personal name Liu Che 劉徹, was probably the most important ruler of the Han dynasty (206 BCE-220 CE). He was a son of Emperor Jing 漢景帝 (r. 157-141 BCE) and Lady Wang 王美人. As a child he was invested as Prince of Jiaodong 膠東. He mounted the throne at the age of sixteen sui and ruled China for half a century.
When Liu Che became emperor, the Han dynasty had already experienced times of hardship an challenged that it had mastered. During that time, there were still several problems to be solved, political issues like the princedoms or the raids of the steppe federation of the Xiongnu 匈奴, as well as economical and financial questions. It was therefore a time for general reforms in the administration and in foreign politics.
In 127 Emperor Wu issued a decree (Tui'enling 推恩令 "Edict concerning the renouncing [of investitures of princedoms] and the benevolent [bestowing of titles]") that thoroughly changed the investiture practice: Titles of prince as well as marquis would in the future not any more endowed with a territory. This practice would ensure that no further territories were cut off from the imperial domain. The princes were from now on strictly controlled by the central government so that it would not any more be possible that princes would join in rebellion, like the Seven Princes had done, or the Princes of Huainan 淮南, Liu An 劉安, and Hengshan 衡山, Liu Ci 劉賜. Owners of a title of nobility were granted a fixed income but were not given own land to live off.
In 122 Emperor Wu used a case of bribery as a excuse to strip off 106 persons of their ranks of nobility. He also restructered the military institutions over which the central government had a direct control, like the Eight Commandants (ba xiaowei 八校尉) or the Palace Guard (yulinjun 羽林軍). The power of the emperor himself was strengthened by circumventing the office of the Counsellor-in-chief (chengxiang 丞相) through memorials from lower officials of the court like palace attendants (shizhong 侍中) or palace stewards (jishizhong 給事中 [sic!]).
Emperor Wu esteemed competence and excellent proposals rather than established offices. He divided the empire into 13 provinces (zhou 州) the officials of which were supervised by a regional inspector (cishi 刺史). So-called "severe officials" (kuli 酷吏) were regularly dispatched to all commanderies to see it that the local officials were doing a good job.
The problem of the Xiongnu raids on Chinese border territory had never been solved during the past decades. The Xiongnu had been appeased by tributary silk and by "peace through marriage" (heqin 和親), a method that required that a (true or faked) princess was sent to the Khan. The advisors of Emperor Wu thought the Han empire sufficiently strong to end this humiliating politics and to challenge the Xiongnu militarily. In 127 general Wei Qing 衛青 attacked the Xiongnu in the region of Yunzhong 雲中, defeated the Princes of Loufan 樓煩王 and Baiyang 白羊王 and occupied a large territory north of the great Yellow River bend, where the commanderies of Shuofang 朔方 and Wuyuan 五原 were established.
In 121 General Huo Qubing 霍去病 made another advance in the region of Longxi 隴西 (modern Gansu), defeated the Khan of the Xiutu 休屠王 at the foots of the Qilian Range 祁連山 and seized the iron statues erected at Mt. Yanqi 焉耆山. He then marched farther into the steppe and forced the Prince of Hunya 渾邪王 to submit. The commanderies of Wuwei 武威, Jiuquan 酒泉， Zhangye 張掖 and Dunhuang 敦煌 were established. In 123 both generals attacked the Xiongnu hordes dwelling in the commanderies of Xiangjun 襄郡 and Daijun 代郡 and pursued them to Mt. Tianyan 寘顔山 and Lake Han 翰海.
The result of these campaigns was that the Xiongnu were repelled into the desert area of the Gobi and were prevented form easily staging raids on Chinese territory. The next step was to look for allies in the west with whose help the Xiongnu could be utterly defeated. Emperor Wu dispatched Zhang Qian 張騫 to establish diplomatic relations with the Tokharians (in Chinese called Yuezhi 月氏). The alliance was not accomplished, but it opened the Han empire the way to the west.
Another area of Chinese expansion was the south of the empire that was at that time still mainly inhabited by native tribes of Austro-Asian origin, like the Min-Yue 閩越 and Dong-Ou 東甌 in Fujian, or the Nanyue 南越 in Guangdong, Guangxi and the north of modern Vietnam. A series of commanderies was established there, and the region came under the direct administration of Han China. The diplomats Tang Meng 唐蒙 and Sima Xiangru 司馬相如 forced the Yi tribes 夷 in the southwest (modern Yunnan) and the Yelang 夜郎, Qiong 邛 and Zuo 筰 in Shu 蜀 (modern Sichuan) to accept the suzerainty of the Han empire. Chinese forces occupied the kingdoms of Qielan 且蘭 and Dian 滇, integrating this area into the Chinese orbit.
The King of Korea, Wei Youqu 衛右渠 (Wi Ugŏ, last ruler of the so-called Wi Man Chosŏn dynasty 衛滿朝鮮), who had killed a high Han official of the commandery of Liaodong 遼東, was forced into submission by a punitive campaign. Also here, the Han established four commanderies.
The continuing campaigns, including the settling down of homeless people in the new commanderies, consumed large amounts of money, so that the state treasury soon fell into a precarious situation. Emperor Wu started selling official titles to increase the state income, began recruting troops from among the peasantry and using the poverty of many peasants that sold themselves as slaves to the government.
The tax burden was increased twofold. The peasants had to deliver a higher amount of grain to the local government, and the central government decided over an issue would decide the financial politics for the next two thousand years: The state monopolized the production and sales of salt and iron and could thereby decicisely increase its income. Coins were furthermore to be cast (sic!) exclusively by the government, and the value of the coins was fixed. Yet it was not only the state who earned a lot from the monopoly, but also merchants granted a licence for this trade, like Kong Jin 孔僅 or Dongguo Xianyang 東郭咸陽. There was a heated debate at the court over the issue of the state monopoly.
Emperor Wu was the first ruler after the First Emperor of Qin 秦始皇 (r. 246-210 BCE) who toured the empire and inspected the local situation especially in the southeast. In 109 he undertook an inspection tour to visit the hydraulic works at the Yellow River dykes that would give a higher security against inundations. He also inspected the works at the Grand Canal 漕渠, the Longshou Canal 龍首渠, the Liufu Canal 六輔渠 and the Baiqu Canal 白渠.
The first few emperors of the Han dynasty had resorted to a politics of laissez-faire that is often linked with the Daoist principle of non-activity (wuwei 無爲). Under Emperor Wu, this situation was changed towards an activist policy in which the state began not only intermingling in economy, but by which certain principles were created according to which a government had to operate.
Emperor Wu adopted Confucianism as the state doctrine and followed the Confucian's rules for a state ritual, like adopting a certain colour for the imperial robes, the offerings at the suburban altars (jiaosi 郊祀), the fengshan 封禪 offerings to Heaven and Earth, for which he climbed Mt. Tai 泰山, ritualised hunting expeditions, and the adoption of reign mottos (niaohao 年號), which became common for all emperors thereafter. He adopted the suggestion of Dong Zhongshu 董仲舒 and Gongsun Hong 公孫弘 to erect a National University (taixue 太學) with erudite (boshi 博士) for the Confucian Classics, and to order all governors to comb their commanderies for worthies and persons of talent that could be brought into officialdom. Emperor Wu thus brought together the tradition of Confucianism and its experts of state rituals with that of legalism and its professionals of administrative and penal law. All other state doctrines were abolished (bachu baijia 罷黜百家 "he expelled the hundred schools of thought").
The personal belief of Emperor Wu can be seen in the general trend of that time that was subject to the so-called Huang-Lao thought 黃老. One aspect of Huang-Lao thought was the belief in immortality, and Emperor Wu was a strong adherent of this tradition. He had several magical practicioners (fangshi 方士) at his court and was impressed by magic and sorcery. In his older years, he was frightened by the thought that someone might cast a spell on him to make him sick and die. This mania led to a great witch-hunt in 91 BCE, during which his Heir Apparent, Prince Wei 衛太子, Liu Ju 劉據, rebelled and died. The capital Chang'an 長安 (modern Xi'an 西安, Shaanxi) was subject to investigation, and more than ten thousand persons were executed as being involved in sorcery.
On his deathbed, Emperor Wu nominated a boy, the eight sui old Liu Fuling 劉弗陵, as his heir (Emperor Zhao 漢昭帝， 87-74 BCE), and ordered a collegium of four persons to assist the future emperor. Huo Guang 霍光, Jin Midi 金日磾 [sic!], Shangguan Jie 上官桀 and Sang Hongyang 桑弘羊 would dominate the court politics for the next decades. Emperor Wu died in 87 BCE, leaving behind a strong and mature empire.