Emperor Wu of Han

As Empress Bo had been deposed one year earlier in 151 BC, the position of empress was left open and Emperor Jing made Consort Wang empress four months later. The seven-year-old Liu Che, now legally the oldest son of the Empress, was made crown prince in 149 BC.

Emperor Wu, already unhappy with his lack of an heir and Empress Chen's spoiled behavior, was further enraged by her mother Princess Liu Piao's greed, that she took a lot from him in everything she did for him. However, Emperor Wu's mother, Empress Dowager Wang, convinced him to tolerate Empress Chen and Liu Piao for the time being, as his aging grandmother was declining physically and would soon die. He spent the next few years pretending to have given up any political ambition, playing the part of a docile hedonist, often sneaking out of the capital Chang'an to engage in hunting and sightseeing and posing as an ordinary nobleman.

In 135 BC, Grand Empress Dowager Dou died, removing the last obstacle against Emperor Wu's ambition for reform.

Yellow line indicates the territory under Qin empire (the dynasty prior to Han). The territory of Han empire (dark orange) before Emperor Wu's reign, the new territory (bright orange) conquered during Emperor Wu's reign (r. 141–87 BC), and combined the largest expansion under Emperor Wu's reign (outlined with wide brown line).

After the death of Grand Empress Dowager Dou in 135 BC, Emperor Wu had full control of the government. While his mother, Empress Dowager Wang, and his uncle Tian Fen were still influential, they lacked the ability to restrain the Emperor's actions.

He first ended the official policy of peace with the Battle of Mayi in 133 BC, which involved a failed plan to trick a force of 30,000 Xiongnu into an ambush of 300,000 Han soldiers. While neither side suffered any casualties, the Xiongnu retaliated by increasing their border attacks, leading many in the Han court to abandon the hope for peace with the Xiongnu.

A famous wrongful execution happened in 117 BC, when the minister of agriculture Yan Yi (颜异), was falsely accused of committing a crime, though he was actually targeted because he had previously offended the emperor by opposing a plan to effectively extort double tributes out of princes and marquesses. Yan was executed for "internal defamation" of the emperor, and this caused the officials to be fearful and willing to flatter the emperor.

Conspirators against Prince Ju included Jiang Chong (江充), the newly appointed head of secret intelligence, who had once had a run-in with Ju after arresting one of his assistants for improper use of an imperial right of way. Another conspirator was Su Wen (蘇文), chief eunuch in charge of caring for imperial concubines, who had previously made false accusations against Ju, claiming he was joyful over Wu's illness and had an adulterous relationship with one of the junior concubines.

Prince Ju sent an individual to impersonate a messenger from Emperor Wu to lure and arrest Jiang and the other conspirators. Su escaped, but Ju accused Jiang of sabotaging his relationship with his father, and personally killed Jiang. With the support of his mother, Ju enlisted his guards, civilians, and prisoners in preparation to defend him.

Su fled to Ganquan Palace and accused Prince Ju of treason. Emperor Wu, not believing it to be true and correctly (at this point) believing that Prince Ju had merely been angry at Jiang, sent a messenger back to Chang'an to summon Prince Ju. The messenger did not dare to proceed to Chang'an, but instead returned and gave Emperor Wu the false report that Prince Ju was conducting a coup. Enraged, Emperor Wu ordered his nephew, Prime Minister Liu Qumao (刘屈犛), to put down the rebellion.

Emperor Wu continued to be enraged and ordered that Prince Ju be tracked down. After a junior official, Linghu Mao (令狐茂), risked his life to speak on Prince Ju's behalf, Emperor Wu's anger began to subside. However, he waited to issue a pardon for Prince Ju.

With the political scene greatly changed, Emperor Wu publicly apologized to the whole nation about his past policy mistakes, a gesture known to history as the Repenting Edict of Luntai (輪台悔詔). The Prime Minister Tian he appointed was in favor of retiring the troops and easing hardships on the people. Tian also promoted agriculture, with several agricultural experts becoming important members of the administration. Wars and territorial expansion generally ceased. These policies and ideals were those supported by Crown Prince Ju, and were finally realised years after his death.

Emperor Wu's political reform resulted in the strengthening of the Emperor's power at expense of the prime minister's authority. The post of Shangshu (court secretaries) was elevated from merely managing documents to that of the Emperor's close advisor, and it stayed this way until the end of the imperial era.

Emperor Wu is one of the most famous emperors of ancient China and has made appearances in quite a lot of Chinese television dramas, examples include:

In the 1991 film "The Addams Family" Morticia Addams donates "a finger trap from the court of Emperor Wu" to a charity auction.