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Wu Zetian

Wu Zetian (17 February 624 – 16 December 705), personal name Wu Zhao, was Empress of China from 660 to 705, ruling first through others and then (from 690) in her own right. She ruled first as empress consort, through her husband Emperor Gaozong and then as an empress dowager, through her sons Emperors Zhongzong and Ruizong, from 660 to 690, not unprecedented in Chinese history. She subsequently founded and ruled as female emperor of the Wu Zhou dynasty of China from 690 to 705. She was the only female sovereign in the history of China widely regarded as legitimate. Under her 45-year reign, China grew larger, becoming one of the great powers of the world, its culture and economy were revitalized, and corruption in the court was reduced. She was eventually removed from power during a coup and died a few months later.

In early life, Wu was the concubine of Emperor Taizong. After his death, she married his ninth son and successor, Emperor Gaozong, officially becoming Gaozong's huanghou (皇后), or empress consort, the highest-ranking of the wives, in 655. Even before becoming empress consort, Wu had considerable political power. Once announced as the empress consort, she began to control the court, and after Gaozong's debilitating stroke in 660, she became administrator of the court, a position equal to the emperor's, until 683.

As a young woman entering Gaozong's harem, Wu competed with Empress Wang and Consort Xiao for the emperor's affection, and eventually expelled and killed them. After her wedding to Gaozong in 655, her rise to power was swift. A strong, charismatic, vengeful, ambitious, well-educated woman who enjoyed her husband's absolute affection, Wu was the most powerful and influential woman at court during a period when the Tang dynasty was at the peak of its glory.

Wu was more decisive and proactive than her husband, and historians consider her to have been the real power behind the throne during Gaozong's reign for more than 20 years until his death. She was partially in control of power from November 660, and totally from January 665. History records that she "was at the helm of the country for long years, her power is no different from that of the emperor." Wu presided over the court with the emperor, and even held court independently when the emperor was unwell. She was given charge of the Heirloom Seal of the Realm, implying that her perusal and consent were necessary before any document or order received legal validity. Gaozong sought her views on all matters before making major decisions. Wu was also granted certain honors and privileges not enjoyed by any Chinese empresses before or since. After Gaozong's death, Wu as empress dowager and regent held power completely and solely, used absolute power more forcefully and violently than before, and suppressed her overt and covert opponents. Seven years later, Wu seized the throne and began the Zhou dynasty, becoming the only empress regnant in Chinese history.

On Emperor Gaozong's death in 683, rather than entering into retirement (as was customary for royal widows), or not interfering in the government (according to the emperor's law, when he reaches the age of 17, he must rule by himself); Wu broke with tradition and took acquisition of complete power, refusing to allow any of her sons to rule. She took the throne in 690 by officially changing the name of the country from Tang to Zhou, changing the name of the royal family from Li to Wu, and holding a formal ceremony to crown herself as emperor.

Empress Wu is considered one of the greatest emperors in Chinese history due to her strong leadership and effective governance, which made China one of the world's most powerful nations. The importance to history of her tenure includes the major expansion of the Chinese empire, extending it far beyond its previous territorial limits, deep into Central Asia, and engaging in a series of wars on the Korean Peninsula, first allying with Silla against Goguryeo, and then against Silla over the occupation of former Goguryeo territory. Within China, besides the more direct consequences of her struggle to gain and maintain power, Wu's leadership resulted in important effects regarding social class in Chinese society and in relation to state support for Taoism, Buddhism, Confucianism, education and literature.

Wu developed a network of spies to build a strong intelligence system in the court and throughout the empire, delivering daily reports on current affairs of the empire or opposition to the central state. She also played a key role in reforming the imperial examination system and encouraging capable officials to work in governance to maintain a peaceful and well-governed state. Effectively, these reforms improved her nation's bureaucracy by ensuring that competence, rather than family connections, became a key feature of the civil service. Wu also had an important impact upon the statuary of the Longmen Grottoes and the "Wordless Stele" at the Qian Mausoleum, as well as the construction of some major buildings and bronze castings that no longer survive. Besides her career as a political leader, Wu also had an active family life. She was a mother of four sons, three of whom also carried the title of emperor, although one held that title only as a posthumous honor. One of her grandsons became the controversial Emperor Xuanzong of Tang, whose reign marked the turning point of the Tang dynasty into sharp decline.

Names and titles
In Chinese history and literature, Wu Zetian was known by various names and titles. Mention of her in the English language has only increased their number. A difficulty in English translations is that they tend to specify gender (as in the case of "emperor" versus "empress" or "prince" versus "princess"), whereas, in Classical Chinese, words such as hou (后, "sovereign", "prince", "queen") or huangdi (皇帝, "imperial supreme ruler", "royal deity") are of grammatically indeterminate gender.

Names
In Wu's time, women's birth names were rarely recorded. She changed her name to Wu Zhao after rising to power, often written as 武曌, (曌 has also been written as 瞾 on occasion, and both are derivatives of 照, which may be her original name), with 瞾 being one of the invented characters by Wu. Wu was her patronymic surname, which she retained, according to traditional Chinese practice, after marriage to Gaozong, of the Li family. Emperor Taizong gave her the art name Wu Mei (武媚), meaning "glamorous". Thus, Chinese people often refer to her as Wu Mei or Wu Meiniang (武媚娘) when they write about her youth, as Wu Hou (武后) when referring to her as empress consort and empress dowager, and as Wu Zetian (武則天) when referring to her as empress regnant.

Titles
During her life, and posthumously, Wu was awarded various official titles. Both hou (后) and huangdi (皇帝) are titles (modifications, or added characters to hou are of lesser importance). Born Wu Zhao, she is not properly known as "Wu Hou" (Empress Wu) until receiving this title in 655, nor is she properly known as "Wu Zetian", her regnal name, until 690, when she took the title Emperor.

 * During the reign of Emperor Gaozu of Tang (618–626):
 * Lady Wu (from 624)
 * During the reign of Emperor Taizong of Tang (626–649):
 * Talented Lady (才人; from 637), 17th rank consort
 * During the reign of Emperor Gaozong of Tang (649–683):
 * Imperial Concubine Zhaoyi (昭儀; from 650), 6th rank consort
 * Empress (皇后; from 655), 1st rank consort
 * Heavenly Empress (天后; from 674), 1st rank consort
 * During the reign of Emperor Zhongzong of Tang (684-684):
 * Empress Dowager Wu (武皇太后; from 683)
 * During the reign of Emperor Ruizong of Tang (684–690)
 * Empress Dowager Wu (武皇太后; from 684)
 * During her reign as the Empress Regnant of the Zhou dynasty (690–705):
 * Holy Emperor (聖神皇帝; from 690)
 * Holy Golden Emperor (金輪聖神皇帝; from 693)
 * Holy Golden Goddess Emperor (越古金輪聖神皇帝; from 694)
 * Holy Golden Emperor (金輪聖神皇帝; from 695)
 * Emperor Tiance Jinlun (天策金輪大帝; from 695)
 * Emperor Zetian Dasheng (則天大聖皇帝; from 705)
 * During the second reign of Emperor Zhongzong of Tang (705–710):
 * Empress Zetian Dasheng (則天大聖皇后; from 705)
 * During the second reign of Emperor Ruizong of Tang (710–712):
 * Heavenly Empress (天后; from 710)
 * Holy Empress (大聖天后; from 710)
 * Empress of Heaven (天后聖帝; from 712)
 * Holy Empress (聖后; from 712)
 * During the reign of Emperor Xuanzong of Tang (713–756):
 * Empress Zetian (則天皇后; from 716)
 * Holy Empress Zetianshun (則天順聖皇后; from 749)

"Empress"
Various Chinese titles have been translated into English as "empress", including "empress" in both the sense of empress consort and empress regnant. Generally, the monarch was male and his chief spouse was given a title such as huanghou (皇后), often translated as "empress" or more specifically "empress consort". Upon the emperor's death, the surviving empress consort could become empress dowager, sometimes wielding considerable political power as regent during the minority of the (male) heir to the position of emperor.

Since the time of Qin Shi Huang (259–210 BC), the Emperor of China using the title huangdi (皇帝, translated as "emperor" or "empress (regnant)" as appropriate), Wu was the only woman in the history of China to assume the title huangdi. Her tenure as de facto ruler of China and official regent of the Tang dynasty (first through her husband and then through her sons, from 665 to 690) was not without precedent in Chinese history, but she broke precedent when she founded her own dynasty in 690, the Zhou (周) (interrupting the Tang dynasty), ruling personally under the name Sacred and Divine Huangdi (聖神皇帝), and variations thereof, from 690 to 705.

Wu Zetian and Empress Dowager Liu of the Song dynasty are said to be the only women in Chinese history to have worn a yellow robe, ordinarily reserved for the emperor's sole use, as a monarch or co-ruler in their own right.

Background and early life

The Wu family clan originated in Wenshui County, Bingzhou (an ancient name of the city of Taiyuan, Shanxi). Wu Zetian's birthplace is not documented in preserved historical literature and remains disputed. Some scholars argue that Wu was born in Wenshui, some that it was Lizhou (利州) (modern-day Guangyuan in Sichuan), while others insist she was born in the imperial capital of Chang'an (today known as Xi'an).

Wu Zetian was born in the seventh year of the reign of Emperor Gaozu of Tang. In the same year, a total eclipse of the sun was visible across China. Her father, Wu Shiyue, worked in the timber business and the family was relatively well off. Her mother was from the powerful Yang family. During the final years of Emperor Yang of Sui, Li Yuan (李淵) (who went on to become Emperor Gaozu of Tang) stayed in the Wu household many times and became close to the Wu family while holding appointments in both Hedong and Taiyuan. After Li Yuan overthrew Emperor Yang, he was generous to the Wu family, giving them money, grain, land, and clothing. Once the Tang dynasty became established, Wu Shihou held a succession of senior ministerial posts, including governor of Yangzhou, Lizhou, and Jingzhou (荊州) (modern-day Jiangling County, Hubei).

Wu was from a wealthy family, and was encouraged by her father to read books and pursue her education. He made sure that she was well-educated, an uncommon trait among women, much less encouraged by their fathers. Wu read and learned about many topics, such as politics and other governmental affairs, writing, literature, and music. At age 14, she was taken to be an imperial concubine (lesser wife) of Emperor Taizong of Tang. It was there that she became a type of secretary. This opportunity allowed her to continue to pursue her education. She was given the title of cairen (才人), the title for one of the consorts with the fifth rank in Tang's nine-rank system for imperial officials, nobles, and consorts. When she was summoned to the palace, her mother, the Lady Yang, wept bitterly when saying farewell to her, but she responded, "How do you know that it is not my fortune to meet the Son of Heaven?" Lady Yang reportedly then understood her ambitions, and therefore stopped crying.

But Consort Wu did not appear to be much favored by Emperor Taizong, though it appears that she did have sexual relations with him at one point. According to her own account (given in a rebuke of Chancellor Ji Xu during her reign), she once impressed Taizong with her fortitude:

"Emperor Taizong had a horse with the name 'Lion Stallion', and it was so large and strong that no one could get on its back. I was a lady in waiting attending Emperor Taizong, and I suggested to him, 'I only need three things to subordinate it: an iron whip, an iron hammer, and a sharp dagger. I will whip it with the iron whip. If it does not submit, I will hammer its head with the iron hammer. If it still does not submit, I will cut its throat with the dagger.' Emperor Taizong praised my bravery. Do you really believe that you are qualified to dirty my dagger?"

When Taizong died in 649, his youngest son, Li Zhi, whose mother was the main wife Wende, succeeded him as Emperor Gaozong. Li Zhi had had an affair with Wu when Taizong was still alive.

Taizong had 14 sons, including three by his beloved Empress Zhangsun (601–636), but none with Consort Wu. Thus, according to the custom by which consorts of deceased emperors who had not produced children were permanently confined to a monastic institution after the emperor's death, Wu was consigned to Ganye Temple (感業寺) with the expectation that she would serve as a Buddhist nun there for the remainder of her life. After Taizong's death, Gaozong met her at the death anniversary of Taizong when he was offering incense. At the time, Consert Xiao and Empress Wang were fighting for favoredness of Gaozong, and Wang asked Gaozong to bring Wu back into the palace, hoping to divert Gaozong's attention. Gaozong agreed and gave Wu the title Lady of Bright Deportment (昭儀). Soon, Gaozong became enamored with Wu, and both Wang and Xiao lost favor.

Rise to power

By early 650, Consort Wu was a concubine of Emperor Gaozong, and was given the title Zhaoyi (昭儀) (Lady of Bright Deportment, the highest-ranking of the nine concubines in the second rank). She progressed rapidly, earning the title of huanghou (皇后) (empress consort, the highest rank and position a woman held in the empire), and gradually gained immeasurable influence and unprecedented authority over the empire's governance throughout Gaozong's reign. Over time, she came to control most major and key decisions made during Gaozong's reign, and presided over imperial gatherings. After Gaozong died in 683, Empress Wu became the empress dowager and regent and power fell completely and solely into her hands. She proceeded to depose Emperor Zhongzong for displaying independence and held onto power even more firmly thereafter. She then had her youngest son, Ruizong, made emperor. She was absolute ruler not only in substance but in appearance. She presided alone over imperial gatherings, prevented Ruizong from taking any active role in governance, and forbade all meetings with him. In 690, she had Ruizong yield the throne to her and established the Zhou dynasty. She ruled as emperor until 705. She was regarded as ruthless in her endeavors to grab power, and was believed by traditional historians to have killed her own children. This was later proven false; these rumors seem to have surfaced 400 years after her death, likely due to the belief in ancient China that a woman was unsuited to hold the power of the emperor. But the cause of death of her first two children is still in question.

Palatial intrigue: (650–655)
Gaozong became emperor at the age of 21. He was not the first choice, as he was inexperienced and frequently incapacitated with a sickness that caused him spells of dizziness. Gaozong was made heir to the empire only due to the disgrace of his two older brothers. On or after the anniversary of Emperor Taizong's death, Gaozong went to Ganye Temple to offer incense to Buddha. When he and Consort Wu saw each other, they both wept. This was seen by Gaozong's wife, Empress Wang. At that time, Gaozong did not favor Wang. Instead, he favored his concubine Consort Xiao. Furthermore, Wang had no children, and Xiao had one son (Li Sujie) and two daughters (Princesses Yiyang and Xuancheng). Wang, seeing that Gaozong was still impressed by Wu's beauty, hoped that the arrival of a new concubine would divert the emperor from Xiao. Therefore, she secretly told Wu to stop shaving her hair and later welcomed her to the palace. (Some modern historians dispute this traditional account. Some think that Wu never left the imperial palace and might have had an affair with Gaozong while Taizong was still alive.)

Wu soon overtook Xiao as Gaozong's favorite. In 652, she gave birth to her first child, a son named Li Hong. In 653, she gave birth to another son, Li Xián. Neither of these sons was in contention to be Gaozong's heir, because Gaozong, at the request of officials influenced by Wang and her uncle (the chancellor Liu Shi), had designated his eldest son Li Zhong as his heir. Li Zhong's mother, Consort Liu, was of lowly birth. Wang did this in order to receive Liu's gratitude.

By 654, both Wang and Xiao had lost favor with Gaozong, and these two former romantic rivals joined forces against Wu, but to no avail. For example, as a sign of his love for Wu, Gaozong conferred posthumous honors on her father, Wu Shiyue, in 654.

In the same year, Wu gave birth to a daughter. But her daughter died shortly after birth, with evidence suggesting deliberate strangulation. The evidence include allegations made by Wu herself, and she accused Wang of murder. Wang was accused of having been seen near the child's room, with corroborating testimony by alleged eyewitnesses. Gaozong was led to believe that Wang, motivated by jealousy, had most likely killed the child. Wang lacked an alibi and was unable to clear her name.

Scientifically credible forensic pathology information about the death of Wu's daughter does not exist, and scholars lack concrete evidence about her death. But scholars have many theories and speculations. Because traditional folklore tends to portray Wu as a power-hungry woman unconcerned about whom she hurt or what she did, the most popular theory is that Wu killed her own child in order to implicate Wang. Other schools of thought argue that Wang indeed killed the child out of jealousy and hatred of Wu. The third argument is that the child died of asphyxiation or crib death. The ventilation systems of the time were nonexistent or of poor quality, and the lack of ventilation combined with using coal as a heating method could have led to carbon monoxide poisoning. In any case, Wu blamed Wang for the girl's death, and as a result, tried to remove Wang from her position.

Because of the child's death, an angry Gaozong also wanted to depose Wang and replace her with Wu. But first he needed to make sure that he had the support of the government chancellors. So Gaozong met with his uncle Zhangsun Wuji, the head chancellor. During the meeting, Gaozong repeatedly brought up Wang's childlessness. Childlessness was a sufficient excuse to depose Wang, but Zhangsun repeatedly found ways to divert the conversation. Subsequent visits made by Wu's mother, Lady Yang, and an official allied with Wu, Xu Jingzong, to seek support from Zhangsun were met with disappointment. Early in 655, he wanted to create Wu, who carried the sixth-highest rank among imperial consorts, Zhaoyi (昭儀, meaning, the lady of the Bright Section), the extraordinary and unprecedented title of Chenfei (宸妃, meaning, the Cosmic Consort), and promote her over all other imperial consorts directly under Wang herself, but Han and fellow chancellor Lai Ji both opposed on the grounds that the title was unprecedented, and so Gaozong did not carry it out. Of course, the evidence shows that he probably granted this title, but it is still unclear.

In summer 655, Wu accused Wang and her mother, Lady Liu, of using witchcraft. In response, Gaozong barred Liu from the palace and demoted Wang's uncle, Liu Shi. Meanwhile, a faction of officials began to form around Wu, including Li Yifu, Xu, Cui Yixuan (崔義玄), and Yuan Gongyu (袁公瑜). Once in the autumn of 655, Gaozong summoned the chancellors Zhangsun, Li Ji, Yu Zhining, and Chu Suiliang to the palace. Chu had deduced that the summons was about changing the empress. Li Ji claimed illness and refused to attend. At the meeting, Chu vehemently opposed deposing Wang, while Zhangsun and Yu showed their disapproval by silence. Meanwhile, chancellors Han Yuan and Lai Ji also opposed the move. When Gaozong asked Li Ji again, he responded, "This is your family matter, Your Imperial Majesty. Why ask anyone else?" Gaozong therefore became resolved. He demoted Chu to commandant at Tan Prefecture (roughly modern Changsha, Hunan), and then deposed both Wang and Xiao. He placed them both under arrest and made Wu empress. (Later that year, Gaozong showed signs of considering their release. Because of this, Wang and Xiao were killed on Empress Wu's orders. After their deaths, they often haunted Wu's dreams.)

For the rest of Gaozong's reign, Wu and Gaozong often took up residence at the eastern capital Luoyang and only infrequently spent time in Chang'an.

Involvement in politics: (655–660)
In 655, Wu became Tang Gaozong's new empress consort (皇后, húanghòu). Empress Wu was a powerful force in the world of politics, and had great influence over the Emperor. After Empress Wu's ascension, one of the first things she did was to submit a petition ostensibly praising the faithfulness of Han and Lai in opposing the unprecedented Chenfei title. The real purpose was to show that she remembered that they had offended her, and it made Han and Lai apprehensive that she was aware of their opposition of her. Han offered to resign soon thereafter, an offer that Emperor Gaozong did not accept.

In 656, on the advice of Xu Jingzong, Emperor Gaozong deposed Consort Liu's son Li Zhong from being his heir apparent. He changed Li Zhong's status to Prince of Liang and designated Empress Wu's son, Li Hong as the title of Prince of Dai and crown prince (that is, Heir Apparent). Soon after, Empress Wu became dominant at court, installing officials who favored her ascension in chancellor posts.

In 657, Empress Wu persuaded Emperor Gaozong to split the empire into two capitals and make Luoyang the capital alongside Chang'an. In 657, Empress Wu and her allies began reprisals against officials who had opposed her ascension. She first had Xu and Li Yifu, who were by now chancellors, falsely accuse Han Yuan and Lai Ji of being complicit with Chu Suiliang in planning treason. The three of them, along with Liu Shi, were demoted to being prefects of remote prefectures, with provisions that they would never be allowed to return to Chang'an. In 659, she had Xu accuse Zhangsun Wuji of plotting treason with the low-level officials Wei Jifang (韋季方) and Li Chao (李巢). Zhangsun was exiled and, later in the year, was forced to commit suicide in exile. Xu further implicated Chu, Liu, Han, and Yu Zhining in the plot as well. Chu, who had died in 658, was posthumously stripped of his titles, and his sons Chu Yanfu (褚彥甫) and Chu Yanchong (褚彥沖) were executed. Orders were also issued to execute Liu and Han, although Han died before the execution order reached his location. It was said that after this time, no official dared to criticize the emperor or empress.

In order to complete the social promotion of her family, she had the Wu clan listed among those of first importance in the registers of the "Great Families" (姓氏錄, xìngshìlù) by changing the "Book of Clans" to "Books of Names"; against imperial traditions. In late 659, she proposed to Emperor Gaozong that Palace Exam be opened to establish talented people from the lower classes as government officials. This reduced the power of the aristocracy. In 660, Li Zhong, Gaozong's first-born son (to consort Liu) also was targeted. Li Zhong had feared that he would be next and had sought out advice of fortune tellers. Wu had him exiled and placed under house arrest.

Ruling with Emperor Gaozong: (660–683)
After removing those who opposed her rise, she had more power to influence politics, and Emperor Gaozong took full advantage of her advice on petitions made by officials and talking about state affairs. In 660, Emperor Gaozong and Empress Wu toured Bian Prefecture (modern-day Taiyuan), and Empress Wu had the opportunity to invite her old neighbors and relatives to a feast. Later that year, Emperor Gaozong began to suffer from an illness that carried the symptoms of painful headaches and loss of vision, generally thought to be hypertension-related. He began to have Empress Wu make rulings on daily petitions and proposals made by officials. It was said that Empress Wu had quick reactions and understood both literature and history, and therefore, she made correct rulings, and Emperor Gaozong, with her ability, no longer paid much attention to governmental affairs, and over time became more and more dependent on her advice, delegating his duties to her. Thereafter, her authority rivaled Emperor Gaozong's. From this point on, Empress Wu became the undisputed power behind the throne until the end of his reign. Slowly, Gaozong became aware of Wu's increasing power, but he could not stop her.

In 661, Empress Wu asked to forbid women from all over the empire to be haiku (entertainers who perform burlesque), and Emperor Gaozong agreed and issued an edict. In April, Gaozong wanted to conquer Goguryeo himself, but surrendered at the urging of Wu and his ministers. In 662, at Wu's suggestion, the imperial consorts' titles were temporarily changed to be devoid of feminine and superficial quality. Her motive was probably to eliminate female rivals. In the same year, Wu selected military generals to attack Goguryeo. During these years, due to favors from Gaozong and Wu, her ally Li Yifu had been exceedingly powerful, and grew particularly corrupt. In 663, after reports of Li Yifu's corruption were made to Gaozong, Gaozong had Liu Xiangdao and Li Ji investigate. They found him guilty. Li Yifu was removed from his post, exiled, and never returned to Chang'an. Wu is said to have been reluctant to accept corruption and therefore did not defend Li Yifu and her only role in Gaozong's decision was to prevent Li Yifu's execution.

Over the years, Empress Wu had repeatedly seen Empress Wang and Consort Xiao in her dreams as they were after death, and she came to believe that their spirits were after her. For that reason, Emperor Gaozong started remodeling a secondary palace, Daming Palace (大明宮), into Penglai Palace (蓬萊宮), and when Penglai Palace's main hall, Hanyuan Hall (含元殿), was completed in 663, Gaozong and Wu moved there. It was later renamed Hanyuan Palace. (Empress Wang and Consort Xiao continued to appear in her dreams even after this, and therefore, late in Gaozong's reign, he and Wu were often at the eastern capital Luoyang, not at Chang'an.)

Over the years, Emperor Gaozong's illness had worsened, and Empress Wu's influence continued to grow and was fully established in the political arena. By 664, Wu was said to be interfering so much in the empire's governance that she was angering Gaozong with her controlling behavior. Furthermore, she had engaged the Taoist sorcerer Guo Xingzhen (郭行真) in using witchcraft—an act prohibited by regulations, which led to Empress Wang's downfall—and the eunuch Wang Fusheng (王伏勝) reported this to Gaozong, angering him further. He consulted the chancellor Shangguan Yi, who suggested that he depose Wu. He had Shangguan draft an edict. But as Shangguan was doing so, Wu received news of what was happening. She went to the emperor to plead her case just as he was holding the edict that Shangguan had drafted. Gaozong could not bear to depose her and blamed the episode on Shangguan. As both Shangguan and Wang had served on Li Zhong's staff, Wu had Xu falsely accuse Shangguan, Wang, and Li Zhong of planning treason. Shangguan, Wang, and Shangguan's son Shangguan Tingzhi (上官庭芝) were executed, while Li Zhong was forced to commit suicide. Shangguan Tingzhi's daughter Shangguan Wan'er, then an infant, and her mother, Lady Zheng, became slaves in the inner palace. After Shangguan Wan'er grew up, she became Empress Wu's trusted secretary.

After that point, Gaozong accepted Wu's participation to a greater extent. From January 665 until the end of his reign, Wu would sit behind a pearl screen behind Gaozong at imperial meetings, and called her own orders "emperor edicts". She even wore the yellow robe of the empire like an emperor, which was extraordinary and unprecedented for an empress. Wu was effectively making the major decisions. After Shangguan Yi's execution, Gaozong increasingly relied on Wu's advice. When chancellors and officials discussed political affairs with him, the first thing he asked was: "Have you discussed this with Empress Wu? What is her opinion?" If she had clear opinions, he would make a decision based on them, and when he was feeling unpleasant, he told the chancellors and officials, "I'm not feeling well. Go to the Empress for work." As a result, imperial powers primarily fell into her hands. According to Song dynasty historian Sīmǎ Guāng 司马光 in the Zizhi Tongjian: "Emperor Gaozong sat enthroned before his ministers as usual while they counseled him, Wu would be parked behind a screen, listening in. It does not matter how vital or insignificant the issue is. The great power of the empire all devolved on the empress. Promotion or demotion, life or death, were settled by her word, The emperor sat with folded arms." She and Gaozong were thereafter referred to as the "Two Saints" (二聖, Er Sheng) both inside the palace and in the empire. The Later Jin historian Liu Xu, in Old Book of Tang, commented:

"When Emperor Gaozong could not listen to the court issues, all affairs were decided by the Empress of Heaven. Since the execution of the Shangguan Yi, she and the emperor appeared together at the court as Sheng (Holy). The Empress of Heaven hung a curtain behind the throne, and all the political affairs were settled by her, and they were called 'two saints' (二聖, Er Sheng) inside and outside. The emperor wanted to issue an edict to make the Empress of Heaven would formally take over the throne of the empire, and Hao Chujun, persuaded him to stop this issue (appoint of regent)."

In 665, Emperor Gaozong and Empress Wu went to Luoyang and began preparation in earnest to make sacrifices to heaven and earth at Mount Tai—a traditional ceremony for emperors that were rarely carried out in history due to the large expenses associated with them. As Wu reasoned that the sacrifice to earth also included sacrifices to past empresses (Gaozong's mother Empress Zhangsun and grandmother Duchess Dou, posthumously honored as an empress), she believed it would be more appropriate to have females offer the sacrifices rather than male officials, as had been tradition in the past. Gaozong decreed that the male ministers would offer sacrifices first, but Wu would do so next, followed by Princess Dowager Yan, the mother of Gaozong's younger brother Li Zhen, the Prince of Yue. In winter 665, Gaozong and Wu headed for Mount Tai. On the lunar new year (10 February 666), they initiated the sacrifices to heaven, which were completed the next day. On 12 February, sacrifices were made to earth. Gaozong and Wu gave general promotions to the imperial officials, and it was said that starting from this time, promotions of imperial officials, which were strict and slow during the reigns of Emperors Gaozu and Taizong, began to become more relaxed and often excessive. Gaozong and Wu also declared a general pardon, except for long-term exiles.

Meanwhile, on account of Empress Wu's almost absolute authority, her mother Lady Yang had been made the Lady of Rong, and her older sister, now widowed, the Lady of Han, and Lady of Rong and Lady of Han wealth surpassed that of all the Chang'an noble families, and they settled in the imperial palace. Her half-brothers Wu Yuanqing and Wu Yuanshuang and cousins Wu Weiliang and Wu Huaiyun, despite the poor relationships that they had with Lady Yang, were promoted and they became extremely rich. But at a feast that Lady Yang held for them, Wu Weiliang offended Lady Yang by stating that they did not find it honorable for them to be promoted on account of Empress Wu. Empress Wu, therefore, ordered to have them demoted to remote prefectures—outwardly to show modesty, but in reality to avenge the offense to her mother. Wu Yuanqing and Wu Yuanshuang died in effective exile. Meanwhile, in or before 666, Lady of Han died as well. Historians attribute Lady of Han death to poisoning at the behest of Empress Wu, as she and the emperor became involved in adultery. After Lady of Han's death, Emperor Gaozong made her daughter the Lady of Wei and considered keeping her in the palace—possibly as a concubine. He did not immediately do so, as he feared that Empress Wu would be displeased. It was said that Empress Wu heard of this and was nevertheless displeased. She had her niece poisoned, by placing poison in food offerings that Wu Weiliang and Wu Huaiyun had made and then blaming them for the death of the Lady of Wei. At Empress Wu command, Wu Weiliang and Wu Huaiyun were executed.

Over the years, Empress Wu had also targeted the children of Emperor Gaozong with his concubines. One of these children was Sujie, the son of Consort Xiao, whom Wu had killed in 655. Early in Gaozong's Qianfeng era (666–668), at Wu's instigation, Gaozong issued an edict that read, "Because Sujie is chronically ill, he is not required to attend imperial gatherings at the capital". In reality, Li Sujie was not ill, and the edict effectively barred him from the capitals Chang'an and Luoyang. Saddened that he was not allowed to see his father, Li Sujie wrote an essay titled "Commentary on Faithfulness and Filial Piety" (忠孝論), which was already lost by the Five Dynasties period. His cashier Zhang Jianzhi secretly submitted the essay to Gaozong. Wu read it, it drew her ire, and she falsely accused Li Sujie of corruption. In 670, Wu's mother, Lady Yang, died, and by Gaozong's and Wu's orders, all of the imperial officials and their wives attended her wake and mourned her. Later that year, with the realm suffering from a major drought, Wu offered to be deposed, which Gaozong rejected. At her request, he further posthumously honored Wu Shiyue (who had previously been posthumously honored as the Duke of Zhou) and Lady Yang by giving them the titles of the Prince and Princess of Taiyuan.

Meanwhile, the son of Empress Wu's older sister the Lady of Han, Helan Minzhi (賀蘭敏之), had been given the surname Wu and allowed to inherit the title of Duke of Zhou. But as it was becoming clear to Empress Wu that he suspected her of murdering his sister, the Lady of Wei, Wu began to take precautions against him. (Helan was also said to have had an incestuous relationship with his grandmother Lady Yang.) In 671, Helan was accused of disobeying mourning regulations during the period of mourning for Lady Yang and raping the daughter of the official Yang Sijian (楊思儉), whom Gaozong and Wu had previously selected to be the wife and crown princess for Li Hong. On Wu's orders, Helan was exiled and either was executed in exile or committed suicide. In 673, Wu provided 20,000 cash for a gigantic statue of Maitreya at Longmen Grottoes. In 674, she had Wu Yuanshuang's son Wu Chengsi recalled from exile to inherit the title of Duke of Zhou.

Although she had real power, Empress Wu was still in the background, and unsatisfied with her position, so took steps to increase the credibility of her power. In 674, one of her claims concerned the title of empress; she argued that because the emperor was called Son of Heaven (天子, Tiānzǐ), his wife should be called Heaven Empress (天后, Tiānhòu). As a result, she linked her rule with divine right. In 675, she succeeded in making her rule popular with the people with "twelve decrees" or "twelve proposals" for better governance and welfare of the people. In middle 675, as Emperor Gaozong's illness worsened, he considered having Wu formally rule as regent. The chancellor Hao Chujun and the official Li Yiyan both opposed this because Wu was already more powerful than Gaozong and they feared that she might take full possession of the throne. As a result, Gaozong did not formally make her regent, and Wu co-ruled with him as divine monarchs until his death in 683. After Hao Chujun opposed her appointment as regent, Wu reduced chancellors' power in state affairs by appointing several scientists as her advisers. She also wanted to diminish the importance of the army, in order to keep it only as a means of "moral education" for the people.

Also in 675, a number of people fell victim to Empress Wu's ire. She had been displeased at the favor that Emperor Gaozong had shown his aunt, Princess Changle. Changle was married to General Zhao Gui (趙瓌) and had a daughter who became the wife and princess consort of Wu's third son, Li Xiǎn, the Prince of Zhou. Princess Zhao was accused of unspecified crimes and placed under arrest, eventually starving to death. Zhao Gui and Changle were exiled. Meanwhile, later that month, Li Hong, the Crown Prince—who urged Wu not to exercise so much influence and authority on Gaozong's governance and offended her by requesting that his half-sisters, Consort Xiao's daughters, Princess Yiyang and Xuancheng (under house arrest) be allowed to marry—died suddenly. Traditional historians generally believed that Wu poisoned Li Hong to death. At her request, Li Xián, then carrying the title of Prince of Yong, was created crown prince. Meanwhile, Consort Xiao's son Li Sujie and another son of Gaozong's, Li Shangjin (李上金), were repeatedly accused of crimes by Wu and were subsequently demoted.

Soon, Empress Wu's relationship with Li Xián also deteriorated because he had become unsettled after hearing rumors that he was not born to her but to her sister, the Lady of Han. When Wu heard of his fearfulness, she became angry with him. She had her literary staff write two works, Good Examples for Shaoyang (少陽正範, "Shaoyang" being an oblique term for a crown prince) and Biographies of Filial Sons (孝子傳) and gave them to Li Xian, and further wrote a number of letters rebuking him, making him more fearful. In 678, contemporary poet Luo Binwang 骆宾王 criticized Wu's involvement in governmental affairs: "She whispered slander from behind her sleeves, and swayed emperor with vixen flirting." Luo's remarks angered Wu and he was dismissed and imprisoned. Furthermore, the sorcerer Ming Chongyan (明崇儼), whom both Wu and Gaozong respected, had said that Li Xián was unsuitable to inherit the throne and was assassinated in 679. The assassins were not caught, making Wu suspect that Li Xián was behind the assassination. Li Xian was also known for his liking of music and women. (Some historians, pointing to oblique references that he was "particularly close" to a number of male servants, also believe that he liked sexual relations with both women and men.) When Wu heard this, she had people report the news to Gaozong. In 680, Li Xián was accused of crimes and during an investigation by the officials Xue Yuanchao, Pei Yan, and Gao Zhizhou, a large number of weaponry was found in his palace. Wu formally accused him of treason and the assassination of Ming. Gaozong wanted to forgive Li Xián for treason, but Wu refused, saying, "Heaven and the world cannot stand the conspiracy against the Son of Heaven. How can he be forgiven? if you do not treat your loved ones with justice, how can you maintain order?" He surrendered at her insistence. Li Xián was deposed and exiled, and at Wu's request, placed under house arrest.

At Empress Wu's request, after the exile of Li Xián, his younger brother Li Xiǎn [similar-sounding name but different Chinese characters] (now renamed Li Zhe) was named crown prince.

In 681, Princess Taiping was married to Xue Shao (薛紹), the son of Emperor Gaozong's sister Princess Chengyang, in a grand ceremony. Empress Wu, initially unimpressed with the lineages of Xue Shao's brothers' wives, wanted to order his brothers to divorce their wives—stopping only after it was pointed out to her that Lady Xiao, the wife of Xue Shao's older brother Xue Yi (薛顗), was a grandniece of the deceased chancellor Xiao Yu. The official Feng Yuanchang was appointed by Gaozong, and he trusted him very much. In 682, Feng also lamented Empress Wu's power and involvement in the administration of the empire and told the emperor: "The queen's authority is very strong, should it be reduced?" Gaozong opposed it, and he was afraid of her, and there was nothing he could do. Upon learning of Feng's ineffective advice to the emperor, Wu became very angry with Feng, and accused him of corruption and degraded him. In 682, Wu pretended to be so friendly that she recalled Shangjin and Sujie and submitted a petition for them to be forgiven their crimes. (Li Shangjin had been previously accused of similar offenses as Li Sujie's and was similarly put under house arrest.) Gaozong made Li Sujie the prefect of Yue Prefecture (岳州, roughly modern Yueyang, Hunan), but she still forbade him and Li Shangjin to visit the capital, and would never allow them to attend political affairs.

In late 683, Gaozong died at Luoyang. At the time of his death, no one was allowed to visit him, and Empress Wu forbade anyone from seeing him, from their children to officials, which led to rumors that she had killed him. Before his death, at Wu's request, he ordered Li Zhe to come to Luoyang, and at her suggestion, handed over the imperial power to Li Zhe. Under her protection, Li Zhe took the throne (as Emperor Zhongzong), but Wu retained the real authority as empress dowager and regent.

Plenipotentiary regent for Emperor Zhongzong
Upon the death of her husband Emperor Gaozong, Wu became empress dowager (皇太后, húangtàihòu) and then regent and she automatically gained full power over the empire. She claimed the senior authority in the empire for herself. Wu exiled other princes so that her third son, Li Zhe, was made heir apparent. Gaozong's will included provisions that Li Zhe should ascend immediately to the imperial throne, Wu would continue to influence all governmental and border matters, and as his father had done, the new emperor should look to Wu in regard to any important matter, military or civil, rewards or penalties, and get her approval. Therefore, Wu remained the sole decision-maker. In the second month of 684, Li Zhe ascended to the imperial throne, known as his temple name Zhongzong, for six weeks.

The new emperor married a woman of the Wei family. The new empress, Empress Wei, sought to place herself in the same position of great authority that Empress Wu had enjoyed.

Under Empress Wei's influence, the emperor appointed his father-in-law as prime minister. He also tried to make his father-in-law Shizhong (侍中, the head of the examination bureau of government, 門下省, Menxia Sheng, and a post considered one for a chancellor) and gave a mid-level office to his wet nurse's son—despite opposition by the chancellor Pei Yan, at one point remarking to Pei:

"What would be wrong even if I gave the empire to Wei Xuanzhen? Why do you care about Shizhong so much?"

Pei reported this to Empress Dowager Wu, and she, after planning with Pei, Liu Yizhi, and the generals Cheng Wuting (程務挺) and Zhang Qianxu (張虔勖), deposed Emperor Zhongzong and replaced him with her youngest son, Li Dan, the Prince of Yu (as Emperor Ruizong). Wu had Zhongzong's father-in-law, Wei Xuanzhen (韋玄貞), brought up on charges of treason. Wei Xuanzhen was sent into seclusion. Zhongzong was reduced to the title of Prince of Luling and exiled. Wu also sent General Qiu Shenji (丘神勣) to Li Xián's place in exile and forced Li Xián to commit suicide.

Plenipotentiary regent for Emperor Ruizong
Wu had her youngest son Li Dan made emperor, known as his temple name Ruizong. Wu was the absolute ruler in both substance and appearance. She did not follow the customary pretense of hiding behind a screen or curtain and, in whispers, issued commands for the nominal ruler to formally announce. Her reign was fully recognized. Ruizong never moved into the imperial quarters, or appeared at imperial function, and remained a virtual prisoner in the inner quarters. He held the title of emperor, but Wu firmly controlled the imperial court, and officials were not allowed to meet with Ruizong, nor was he allowed to rule on matters of state. It was to Wu that officials reported, with Ruizong not even nominally approving official actions. Soon after Ruizong took the throne, Wu carried out a major renaming of governmental offices and banners. Wu elevated Luoyang's status, making it a coequal capital. At her nephew Wu Chengsi's suggestion, she expanded the shrine of the Wu ancestors and gave them greater posthumous honors, and made Wu's ancestral shrine the size of the emperor's ancestral shrine.

Soon thereafter, Li Ji's grandson Li Jingye, the Duke of Ying, who had been disaffected by his own exile, started a rebellion at Yang Prefecture (揚州, roughly modern Yangzhou, Jiangsu). The rebellion initially drew popular support in the region, but Li Jingye progressed slowly in his attack and did not take advantage of that support. Meanwhile, Pei suggested to Empress Dowager Wu that she return imperial authority to the Emperor, arguing that doing so would cause the rebellion to collapse on its own. This offended Wu, and she accused him of being complicit with Li Jingye and had him executed; she also demoted, exiled, and killed a number of officials who, when Pei was arrested, tried to speak on his behalf. She sent General Li Xiaoyi (李孝逸) to attack Li Jingye, and while Li Xiaoyi was initially unsuccessful, he pushed on at the urging of his assistant Wei Yuanzhong and eventually crushed Li Jingye's forces. Li Jingye fled and was killed in flight.

By 685, Empress Dowager Wu was having an affair with the Buddhist monk Huaiyi, and over the next few years, Huaiyi received progressively greater honors. In 686, Wu offered to return imperial authorities to Emperor Ruizong, but Ruizong, knowing that she did not truly intend to do so, declined, and she continued to exercise imperial authority. Meanwhile, she installed copper mailboxes outside the imperial government buildings to encourage the people of the realm to report secretly on others, as she suspected many officials of opposing her. Wu personally read all the reports of betrayal. Secret police officials, including Suo Yuanli, Zhou Xing, and Lai Junchen, began to rise in power and carry out systematic false accusations, torture, and executions.

In 688, Empress Dowager Wu was set to make sacrifices to the deity of the Luo River (洛水, flowing through the Henan province city of Luoyang, then the "Eastern Capital"). She summoned senior members of Tang's Li imperial clan to Luoyang. Worried that she planned to slaughter them and secure the throne for herself, the imperial princes plotted to resist her. But before a rebellion could be comprehensively planned, Li Zhen and his son Li Chong, the Prince of Langye rose first, at their respective posts as prefects of Yu Prefecture (豫州, roughly modern Zhumadian, Henan) and Bo Prefecture (博州, roughly modern Liaocheng, Shandong). The other princes were not yet ready, and did not rise, and forces sent by Empress Dowager Wu and the local forces crushed Li Chong and Li Zhen's forces quickly. Wu took this opportunity to arrest Emperor Gaozong's granduncles Li Yuanjia (李元嘉) the Prince of Han, Li Lingkui (李靈夔) the Prince of Lu, and Princess Changle, as well as many other members of the Li clan, and forced them to commit suicide. Even Princess Taiping's husband Xue Shao was implicated and starved to death. In the subsequent years, there continued to be many politically motivated massacres of officials and Li clan members.

In 690, Wu took the final step to become the empress regnant of the newly proclaimed Zhou dynasty, and the title Huangdi. Traditional Chinese order of succession (akin to the Salic law in Europe) did not allow a woman to ascend the throne, but Wu was determined to quash the opposition and the use of the secret police continued after she took the throne. While her organization of the civil service system was criticized for its laxity of the promotion of officials, Wu was still considered capable of evaluating the officials' performance once they were in office. The Song dynasty historian Sima Guang, in his Zizhi Tongjian, writes: "Even though the Empress Dowager excessively used official titles to cause people to submit to her, if she saw that someone was incompetent, she would immediately depose or even execute him. She grasped the powers of punishment and award, controlled the state, and made her own judgments as to policy decisions. She was observant and had good judgment, so the talented people of the time also were willing to be used by her."

Reign as empress regnant
In 690, Wu had Emperor Ruizong yield the throne to her and established the Zhou dynasty, with herself as the imperial ruler (Huangdi).

The early part of her reign was characterized by secret police terror, which moderated as the years went by. On the other hand, she was recognized as a capable and attentive ruler even by traditional historians who despised her, and her ability to select capable men to serve as officials was admired for the rest of the Tang dynasty as well as in subsequent dynasties.

Wu Zetian's reign was a pivotal moment for the imperial examination system. The reason for this was because up until that point, the Tang rulers had all been male members of the Li family. Wu Zetian, who officially took the title of emperor in 690, was a woman outside the Li family who needed an alternative base of power. Reform of the imperial examinations featured prominently in her plan to create a new class of elite bureaucrats derived from humbler origins. Both the palace and military examinations were created under Wu Zetian which were based solely on merit.

Early reign (690–696)

Shortly after Wu took the throne in her newly established dynasty, she elevated the status of Buddhism above that of Taoism. She officially sanctioned Buddhism by building temples named Dayun Temple (大雲寺) in each prefecture belonging to the capital regions of the two capitals, Luoyang and Chang'an, and created nine senior monks as dukes. She enshrined seven generations of Wu ancestors at the imperial ancestral temple, while continuing to offer sacrifices to the Tang emperors Gaozu, Taizong, and Gaozong.

Wu faced the issue of succession. At the time she took the throne, she created Li Dan, the former Emperor Ruizong, crown prince, and bestowed the name Wu on him. The official Zhang Jiafu convinced the commoner Wang Qingzhi (王慶之) to start a petition drive to make her nephew Wu Chengsi crown prince, arguing that an emperor named Wu should pass the throne to a member of the Wu clan. Wu Zetian was tempted to do so, and when the chancellors Cen Changqian and Ge Fuyuan opposed sternly, they, along with fellow chancellor Ouyang Tong, were executed. She ultimately declined Wang's request to make Wu Chengsi crown prince, but for a time allowed Wang to freely enter the palace to see her.

On one occasion, when Wang angered her by coming to the palace too much, she asked the official Li Zhaode to batter Wang as punishment. Li Zhaode exploited the opportunity to batter Wang to death, and his group of petitioners scattered. Li Zhaode then persuaded Wu Zetian to keep Li Dan as crown prince—pointing out that a son was closer in relations than a nephew, and that if Wu Chengsi became emperor, Gaozong would never again be worshiped. Wu Zetian agreed, and for some time did not reconsider the matter. At Li Zhaode's warning that Wu Chengsi was becoming too powerful, Wu Zetian stripped Wu Chengsi of his chancellor authority and bestowed on him largely honorific titles without authority.

Meanwhile, the secret police officials' power continued to increase, until they appeared to be curbed, starting in about 692, when Lai Junchen was foiled in his attempt to have the chancellors Ren Zhigu, Di Renjie, Pei Xingben, and other officials Cui Xuanli (崔宣禮), Lu Xian (盧獻), Wei Yuanzhong, and Li Sizhen (李嗣眞) executed. Di, under arrest, had hidden a secret petition inside a change of clothes and had it submitted by his son Di Guangyuan (狄光遠). The seven were exiled. After this incident, particularly at the urging of Li Zhaode, Zhu Jingze, and Zhou Ju (周矩), the waves of politically motivated massacres decreased, although they did not end entirely. Wu Zetian utilized the imperial examination system to find talented poor people or people without backgrounds to stabilize her regime.

Also in 692, Wu Zetian commissioned the general Wang Xiaojie to attack the Tibetan Empire. Wang recaptured the four garrisons of the Western Regions that had fallen to the Tibetan Empire in 670 – Kucha, Yutian, Kashgar, and Suyab.

In 693, after Wu's trusted lady-in-waiting Wei Tuan'er (韋團兒), who hated Li Dan because he rejected her advances, falsely accused Li Dan's wife Crown Princess Liu and Consort Dou of using witchcraft, Wu had Crown Princess Liu and Consort Dou killed. Li Dan, fearful that he was next, did not dare speak of them. When Wei planned to falsely accuse Li Dan, someone informed on her, and she was executed. Wu had Li Dan's sons demoted in their princely titles. When the officials Pei Feigong (裴匪躬) and Fan Yunxian (范雲仙) were accused of secretly meeting Li Dan, she executed Pei and Fan and further barred officials from meeting Li Dan.

There were then accusations that Li Dan was plotting treason. Under Wu's direction, Lai launched an investigation. He arrested Li Dan's servants and tortured them. The torture was such that many of them were ready to falsely implicate themselves and Li Dan. One of Li Dan's servants, An Jincang, proclaimed Li Dan's innocence and cut his own belly open to swear to that fact. When Wu heard what An did, she had doctors attend to An and barely saved his life, and then ordered Lai to end the investigation, saving Li Dan.

In 694, Li Zhaode, who had become powerful after Wu Chengsi's removal, was thought to be too powerful, and Wu Zetian removed him. Also around this time, she became highly impressed with a group of mystic individuals—the hermit Wei Shifang (on whom she bestowed a chancellor title briefly), who claimed to be more than 350 years old; an old Buddhist nun who claimed to be a Buddha and capable of predicting the future; and a non-Han man who claimed to be 500 years old. During this time, Wu briefly claimed to be and adopted the cult imagery of Maitreya in order to build popular support for her reign.

In 695, after the imperial meeting hall (明堂) and the Heavenly Hall (天堂) were burned by Huaiyi, who was jealous at Wu's taking another lover, the imperial physician Shen Nanqiu (沈南璆), Wu became angry at these mystics for failing to predict the fire. The old nun and her students were arrested and made into slaves. Wei committed suicide. The old non-Han man fled. Wu put Huaiyi to death. After this incident, she appeared to pay less attention to mysticism and became even more dedicated than before to the affairs of state.

Middle reign (696–701)
Wu's administration soon faced various troubles on the western and northern borders. In spring 696 she sent an army commanded by Wang Xiaojie and Lou Shide against the Tibetan Empire, which was soundly defeated by Tibetan generals, the brothers Gar Trinring Tsendro (論欽陵) and Gar Tsenba (論贊婆). As a result, she demoted Wang to commoner rank and Lou to a low-level prefectural official, though she eventually restored both to general positions. In April of the same year, Wu recast the Nine Tripod Cauldrons, the symbol of ultimate power in ancient China, to reinforce her authority.

A much more serious threat arose in summer 696. The Khitan chieftains Li Jinzhong and Sun Wanrong, brothers-in-law, angry over the mistreatment of the Khitan people by the Zhou official Zhao Wenhui (趙文翽), the prefect of Ying Prefecture (營州, roughly Zhaoyang County, Liaoning), rebelled, with Li assuming the title of Wushang Khan (無上可汗). Armies that Wu sent to suppress Li and Sun's rebellion were defeated by Khitan forces, which attacked Zhou proper. Meanwhile, Qapaghan Qaghan of the Second Turkic Khaganate offered to submit, while also launching attacks against Zhou and Khitan. The attacks included one against the Khitan base of operations during the winter of 696, shortly after Li's death, which resulted in the capturing of Li's and Sun's families and temporarily halted Khitan operations against Zhou.

Sun, after taking over as khan and reorganizing Khitan forces, again attacked Zhou territory and had many victories over Zhou forces, including a battle during which Wang Shijie was killed. Wu tried to allay the situation by making peace with Ashina Mochuo on fairly costly terms—the return of Tujue people who had previously submitted to Zhou and providing Mochuo with seeds, silk, tools, and iron. In summer 697, Mochuo launched another attack on Khitan's base of operations, and this time, after his attack, Khitan forces collapsed and Sun was killed in flight, ending the Khitan threat.

Meanwhile, also in 697, Lai Junchen, who had at one point lost power but then returned to power, falsely accused Li Zhaode (who had been pardoned) of crimes, and then planned to falsely accuse Li Dan, Li Zhe, the Wu clan princes, and Princess Taiping of treason. The Wu clan princes and Princess Taiping acted first against him, accusing him of crimes, and he and Li Zhaode were executed together. After Lai's death, the secret police's reign largely ended. Gradually, many of the victims of Lai and the other secret police officials were exonerated posthumously. Meanwhile, around this time, Wu began relationships with two new lovers—the brothers Zhang Yizhi and Zhang Changzong, who became honored within the palace and were eventually created dukes.

Around 698, Wu Chengsi and another nephew of Wu Zetian's, Wu Sansi, the Prince of Liang, repeatedly made attempts to have officials persuade Wu Zetian to make one of them crown prince—again arguing that an emperor should pass the throne to someone of the same clan. But Di Renjie, who by now had become a trusted chancellor, firmly opposed the idea, and proposed that Li Zhe be recalled instead. He was supported in this by fellow chancellors Wang Fangqing and Wang Jishan, as well as Wu Zetian's close advisor Ji Xu, who further persuaded the Zhang brothers to support the idea. In spring 698, Wu agreed and recalled Li Zhe from exile. Soon, Li Dan offered to yield the crown prince position to Li Zhe, and Wu created Li Zhe crown prince. She soon changed his name back to Li Xiǎn and then Wu Xian.

Later, Ashina Mochuo demanded a Tang dynasty prince for marriage to his daughter, part of a plot to join his family with the Tang, displace the Zhou, and restore Tang rule over China, under his influence. When Wu sent a member of her own family, grandnephew Wu Yanxiu (武延秀), to marry Mochuo's daughter instead, he rejected him. Mochuo had no intention to cement the peace treaty with a marriage. Instead, when Wu Yanxiu arrived, he detained him and then launched a major attack on Zhou, advancing as far south as Zhao Prefecture (趙州, in modern Shijiazhuang, Hebei) before withdrawing.

In 699, the Tibetan threat ceased. Emperor Tridu Songtsen, unhappy that Gar Trinring was monopolizing power, slaughtered Trinring's associates when Trinring was away from Lhasa. He then defeated Trinring in battle, and Trinring committed suicide. Gar Tsenba and Trinring's son, Lun Gongren (論弓仁), surrendered to Zhou. After this, the Tibetan Empire underwent internal turmoil for several years, and there was peace for Zhou in the border region.

Also in 699, Wu, realizing that she was growing old, feared that after her death, Li Xian and the Wu clan princes would not have peace with each other. She made him, Li Dan, Princess Taiping, Princess Taiping's second husband Wu Youji (a nephew of hers), the Prince of Ding, and other Wu clan princes to swear an oath to each other.

Late reign (701–705)

As Wu grew older, Zhang Yizhi and Zhang Changzong became increasingly powerful, and even the princes of the Wu clan sought their favour. She increasingly relied on them to handle the affairs of state. This was secretly discussed and criticized by her grandson Li Chongrun, the Prince of Shao (Li Xian's son), granddaughter Li Xianhui (李仙蕙) the Lady Yongtai (Li Chongrun's sister), and Li Xianhui's husband Wu Yanji (武延基) the Prince of Wei (Wu Zetian's grandnephew and Wu Chengsi's son). Somehow the discussion was leaked, and Zhang Yizhi reported this to Wu. She ordered the three of them to commit suicide.

Despite her age, Wu continued to be interested in finding talented officials and promoting them. People she promoted in her old age included Cui Xuanwei and Zhang Jiazhen.

By 703, Zhang Yizhi and Zhang Changzong had become resentful of Wei Yuanzhong, who by now was a senior chancellor, for dressing down their brother Zhang Changyi (張昌儀) and rejecting the promotion of another brother, Zhang Changqi (張昌期). They also were fearful that if Wu died, Wei would find a way to execute them, and therefore accused Wei and Gao Jian (高戩), an official favored by Princess Taiping, of speculating on Wu's old age and death. They initially got Wei's subordinate Zhang Shuo to agree to corroborate the charges, but once Zhang Shuo was before Wu, he instead accused Zhang Yizhi and Zhang Changzong of forcing him to bear false witness. As a result, Wei, Gao, and Zhang Shuo were exiled, but escaped death.

Removal and death

In autumn 704, accusations of corruption began to be levelled against Zhang Yizhi and Zhang Changzong, as well as their brothers Zhang Changqi, Zhang Changyi, and Zhang Tongxiu (張同休). Zhang Tongxiu and Zhang Changyi were demoted, but even though the officials Li Chengjia (李承嘉) and Huan Yanfan advocated that Zhang Yizhi and Zhang Changzong be removed as well, Wu Zetian, taking the suggestion of the chancellor Yang Zaisi, did not do so. Subsequently, charges of corruption against Zhang Yizhi and Zhang Changzong were renewed by the chancellor Wei Anshi.

In winter 704, Wu Zetian became seriously ill for a period, and only the Zhang brothers were allowed to see her; the chancellors were not. This led to speculation that Zhang Yizhi and Zhang Changzong were plotting to take over the throne, and there were repeated accusations of treason. Once her condition improved, Cui Xuanwei advocated that only Li Xian and Li Dan be allowed to attend to her—a suggestion she did not accept. After further accusations against the Zhang brothers by Huan and Song Jing, Wu allowed Song to investigate, but before the investigation was completed, she issued a pardon for Zhang Yizhi, derailing Song's investigation.

By spring 705, Wu was seriously ill again. Zhang Jianzhi, Jing Hui, and Yuan Shuji planned a coup to kill the Zhang brothers. They convinced the generals Li Duozuo, Li Dan (李湛, note different character than the former emperor), and Yang Yuanyan (楊元琰) and another chancellor, Yao Yuanzhi, to be involved. With agreement from Li Xian as well, they acted on 20 February, killing Zhang Yizhi and Zhang Changzong, and had Changsheng Hall (長生殿), where Wu was residing, surrounded. They then reported to her that the Zhang brothers had been executed for treason, and forced her to yield the throne to Li Xian. On 21 February, an edict was issued in her name that made Li Xian regent, and on 22 February, an edict was issued in her name passing the throne to him. On 23 February, Li Xian formally retook the throne, and the next day, under heavy guard, Wu was moved to the subsidiary palace, Shangyang Palace (上陽宮), while still honored with the title of Empress Regent Zetian Dasheng (則天大聖皇帝). On 3 March, the Tang dynasty was restored, ending the Zhou.

Wu died on 16 December, and, pursuant to a final edict issued in her name, was no longer called empress regnant, but instead "Empress Consort Zetian Dasheng" (則天大聖皇后). In 706, Wu's son Emperor Zhongzong had his father, Emperor Gaozong and Wu interred in a joint burial at the Qianling Mausoleum, near the capital Chang'an on Mount Liang. Zhongzong also buried at Qianling his brother Li Xián, son Li Chongrun, and daughter Li Xianhui (李仙蕙) the Lady Yongtai (posthumously honored as the Princess Yongtai)—victims of Wu's wrath.

Wu Zhou dynasty

In 690, Wu Zetian founded the Wu Zhou dynasty, named after the historical Zhou dynasty (1046–256 BC). The traditional historical view is to discount the Wu Zhou dynasty: dynasties by definition involve the succession of rulers from one family, and the Wu Zhou dynasty was founded by Wu and ended within her lifetime, with her abdication in 705. The alternative is to view the Wu Zhou dynasty as the revival of the historical Zhou dynasty, which was ruled (at least nominally) by the Ji family, almost a thousand years before. Either way, the Wu Zhou dynasty was a brief interruption of the Li family's Tang dynasty, not a fully realized dynasty. But Wu's claim to found a new dynasty was little opposed at the time (690). The 15-year period that Wu designated as her "Zhou dynasty", considered in the context of nearly a half century of de facto and de jure rule (c. 654–705), reveals a remarkable and still debated period of history. In this context, designating a new dynasty with her as emperor can be seen as part of her power politics and as the culmination of her rule. Though Wu's Zhou dynasty had its own notable characteristics, they are difficult to separate from Wu's reign of power, which lasted for about half of a century.

Wu's consolidation of power in part relied on a system of spies. She used informants to choose people to eliminate, a process that peaked in 697 with the wholesale demotion, exile, or killing of various aristocratic families and scholars, furthermore prohibiting their sons from holding office.

Wu eliminated many of her real, potential, or perceived rivals to power by means of death (including execution, suicide by command, and more or less directly killing people), demotion, and exile. Mostly this was carried out by her secret police, led by people like Wao Ganjun and Lai Junchen, who were known to have written the Manual of Accusation, a document detailing steps for interrogation and obtaining confessions by torture. One of these methods, the "Dying Swine's Melancholy" (死猪愁), which merely indicated a level of pain inflicted by a torture device, seems to have been conflated in the years following Wu's death with the story of the "human swine" torture conducted by Empress Lü Zhi, in which her victim had her eyes gouged out, hands and feet chopped off, ears burnt, and was imprisoned in a latrine.

Wu targeted various people, including many in her own family. In reaction to an attempt to remove her from power, in 684, she massacred 12 entire collateral branches of the imperial family. Besides this, she also altered the ancient balance of power in China dating to the Qin dynasty. The old area of the Qin state was later called Guanzhong—literally, the area "within the fortified mountain passes". From this area of northwest China, the Ying family of Qin arose, unifying China into its first historical empire. During the Han dynasty, Sima Qian records in his Shiji that Guanzhong had three-tenths of China's population but six-tenths of its wealth. Additionally, at the beginning of Wu's ascendency, Guanzhong was still the stronghold of the most nationally powerful aristocratic families, even though economic development in other parts of China had improved the lot of families in other regions. The Guangzhong aristocracy was not willing to relinquish its hold on the reins of government, but some of the more newly wealthy families in other areas, such as the North China Plain or Hubei, were eager for a larger share of national power. Most of the opposition to Wu was from the Guangzhong families of northwest China. Accordingly, she repressed them, instead favoring less privileged families, thus raising to the ranks of power many talented but less aristocratic families, often recruited through the official examination system. Many of those so favored originated from the North China plain. Through a process of eliminating or diminishing the power of the established aristocracy, whom she perceived as disloyal to her, and establishing a reformed upper class in China loyal to her, Wu made major social changes that historians are still evaluating. Many of Wu's measures were popular and helped her to gain support for her rule. Wu came to power during a time in China in which the people were fairly contented, the administration was run well, and the economy was characterized by rising living standards. For the most part, as far as the masses were concerned, Wu continued in this manner. She was determined that free, self-sufficient farmers continue to work their own land, so she periodically used the juntian, equal-field system, together with updated census figures to ensure fair land allocations, reallocating as necessary. Much of her success was due to her various edicts (including those known as her "Acts of Grace"), which helped satisfy the needs of the lower classes through various acts of relief, her widening recruitment to government service to include previously excluded gentry and commoners, and her generous promotions and pay raises for the lower ranks.

Wu used her military and diplomatic skills to enhance her position. The fubing system of self-supportive soldier-farmer colonies, which provided local militia and labor services for her government, allowed her to maintain her armed forces at reduced expense. She also pursued a policy of military action to expand the empire to its furthest extent ever up to that point in Central Asia. Expansion efforts against Tibet and to the northwest were less successful. Allying with the Korean kingdom of Silla against Goguryeo with the promise of ceding Goguryeo's territory to Silla, Chinese forces occupied Goguryeo after its defeat, and even began to occupy Silla territory. Silla resisted the imposition of Chinese rule, and by allying with Goguryeo and Baekche, was able to expel its former ally from the peninsula. Hong argues that Silla's success was in part due to a shift in Wu's focus to Tibet and inadequate support for the forces in the Korean peninsula. In 694, Wu's forces decisively defeated the Tibetan–Western Turk alliance and retook the Four Garrisons of Anxi.

In 651, shortly after the Muslim conquest of Persia, the first Arab ambassador arrived in China.

Reform of the imperial examination system
One apparatus of government that fell into Wu's power was the imperial examination system, the basic theory and practice of which was to recruit into government service those men who were the best educated, most talented, and had the best potential to perform their duties, and to do so by testing a pool of candidates to determine this. This pool was male only, and the qualified pool of candidates and resulting placements into official positions was on a relatively small scale at the time Wu took control of government. The official tests examined things considered important for functionaries of the highly developed, bureaucratic government structure of the imperial government, such as level of literacy in terms of reading and writing and possession of the specific knowledge considered necessary and desirable for a governmental official, such as Confucian precepts on the nature of virtue and theory on the proper ordering of and relationships within society. Wu continued to use the imperial examination system to recruit civil servants, and introduced major changes to the system she inherited, including increasing the pool of candidates permitted to take the test by allowing commoners and gentry, previously disqualified by their background, to take it. In 693, she expanded the governmental examination system and greatly increased the importance of this method of recruiting government officials. Wu provided increased opportunity for the representation within government to people of the North China Plain versus people of the northwestern aristocratic families (whom she decimated, anyway); and the successful candidates recruited through the examination system became an elite group within her government. The historical details of the consequences of Wu's promoting a new group of people from previously disenfranchised backgrounds into prominence as powerful governmental officials, and the examination system's role, remain debated by scholars of this subject.

The Great Cloud Sutra
Wu Zetian used her political powers to harness from Buddhist practices a strategy to build sovereignty and legitimacy to her throne while decisively establishing the Zhou dynasty in a society under Confucian and patriarchal ideals. One of the first steps she took to legitimize her ascension to the throne was to proclaim herself as the reincarnation of the Devi of Pure Radiance (Jingguang tiannü) through a series of prophecies. In 690, Wu sought out the support of the monk Xue Huaiyi, her reputed lover, and other nine orthodox Buddhist monks, to compose the apocryphal Commentary on the Meanings of the Prophecies About the Divine Sovereign in the Great Cloud Sutra (Dayunjing Shenhuang Shouji Yishu). Translated from a late fourth-century version in Sanskrit to Chinese, the original Great Cloud Sutra (Dayunjing) accentuated in Wu's Commentary had fascicles describing a conversation between the Buddha and the Devi of Pure Radiance. In the sutra, the Buddha foretells to Jingguang that he would be a bodhisattva reincarnated in a woman's body in order to convert beings and rule over the territory of a country. Wu's Buddhist supporters meticulously propagated the Commentary "on the eve of her accession to the dragon throne" while seeking to justify the various events that led Wu to occupy the position of Huangdi as a female ruler and bodhisattva. Since gender in the Buddhist Devi worlds have no standard form, Wu later took a further step to transcend her gender limitations by identifying herself as the incarnation of two important male Buddhist divinities, Maitreya and Vairocana. Her narrative was intentionally crafted to persuade the Confucian establishment, circumvent the Five Impediments that restricted women from holding political and religious power, and gain public support.

Sacrifice on Mount Tai
In relation to Daoism, there are records that point to Wu's participation in important religious rituals, such as the tou long on Mount Song, and feng and shan on Mount Tai. One of the most important rituals was performed in 666. When Emperor Gaozong offered sacrifices to the deities of heaven and earth, Wu, in an unprecedented action, offered sacrifices after him, with Princess Dowager Yan, mother of Gaozong's brother Li Zhen, Prince of Yue, offering sacrifices after her. Wu's procession of ladies up Mount Tai conspicuously linked Wu with the Chinese empire's most sacred traditional rites. Another important performance was made in 700, when Wu conducted the tou long Daoist expiatory rite. Her participation in the rituals had political as well as religious motives. Such ceremonies served to consolidate Wu's life in politics and show she possessed the Mandate of Heaven.

North Gate Scholars
Toward the end of Gaozong's life, Wu began engaging a number of mid-level officials who had literary talent, including Yuan Wanqing (元萬頃), Liu Yizhi, Fan Lübing, Miao Chuke (苗楚客), Zhou Simao (周思茂), and Han Chubin (韓楚賓), to write a number of works on her behalf, including the Biographies of Notable Women (列女傳), Guidelines for Imperial Subjects (臣軌), and New Teachings for Official Staff Members (百僚新誡). Collectively, they became known as the "North Gate Scholars" (北門學士), because they served inside the palace, which was north of the imperial government buildings, and Wu sought advice from them to divert the powers of the chancellors.

The "Twelve Suggestions"
Around the new year 675, Wu submitted 12 suggestions. One was that the work of Laozi (whose family name was Li and to whom the Tang imperial clan traced its ancestry), Tao Te Ching, should be added to imperial university students' required reading. Another was that a three-year mourning period should be observed for a mother's death in all cases, not just in cases when the father was no longer alive. Emperor Gaozong praised her suggestions and adopted them.

Modified Chinese characters

In 690, Wu's cousin's son Zong Qinke submitted a number of modified Chinese characters intended to showcase Wu's greatness. She adopted them, and took one of the modified characters, Zhao (曌), to be her formal name (i.e., the name by which the people would exercise naming taboo on). 曌 was made from two other characters: Ming (明) on top, meaning "light" or "clarity", and Kong (空) on the bottom, meaning "sky". The implication appeared to be that she would be like the light shining from the sky. (Zhao (照), meaning "shine", from which 曌 was derived, might have been her original name, but evidence of that is inconclusive.) Later that year, after successive petition drives started by the low-level official Fu Youyi began to occur in waves, asking her to take the throne, Emperor Ruizong offered to take the name of Wu as well. On 18 August 690, she approved the requests. She changed the state's name to Zhou, claiming ancestry from the Zhou dynasty, and took the throne as Empress Regnant (with the title Empress Regnant Shengshen (聖神皇帝), literally "Divine and Sacred Emperor or Empress Regnant"). Ruizong was deposed and made crown prince with the atypical title Huangsi (皇嗣). This thus interrupted the Tang dynasty, and Wu became the first (and only) woman to reign over China as empress regnant.

Poetry
Wu's court was a focus of literary creativity. Forty-six of Wu's poems are collected in the Complete Tang Poems and 61 essays under her name are recorded in the Quan Tangwen (Collected Tang Essays). Many of those writings serve political ends, but there is one poem in which she laments her mother after she died and expresses her despair at not being able to see her again.

During Wu's reign, the imperial court produced various works of which she was a sponsor, such as the anthology of her court's poetry known as the Zhuying ji (Collection of Precious Glories), which contained poems by Cui Rong, Li Jiao, Zhang Yue, and others, arranged according to the poets' rank at court. Among the literary developments that took place during Wu's time (and partly at her court) was the final stylistic development of the "new style" poetry of the regulated verse (jintishi), by the poetic pair Song Zhiwen and Shen Quanqi.

Wu also patronized scholars by founding an institute to produce the Collection of Biographies of Famous Women. The development of what is considered characteristic Tang poetry is traditionally ascribed to Chen Zi'ang, one of Wu's ministers.

Literary allusions
Literary allusions to Wu may carry several connotations: a woman who has inappropriately overstepped her bounds, the hypocrisy of preaching compassion while simultaneously engaging in a pattern of political corruption and vicious behavior. For many centuries, the establishment used Wu as an example of what can go wrong when a woman is in charge.

Mao Zedong's wife Jiang Qing rehabilitated Wu as part of a propaganda campaign to suggest she be considered as a successor to her ailing husband. Frank Dikotter asserted that Jiang Qing "had started to compare herself to the only empress ever to have ruled in Chinese history, namely Wu Zetian. Articles praising the sixth-century empress as a great unifier of the nation appeared in the press, even though she was popularly reviled as a ruthless, wicked ruler who had mercilessly crushed her opponents." However, Dikotter did not cite sources for his claim.

In his biography Wu, Jonathan Clements writes that these wildly differing uses of a historical figure often led to contradictory and even hysterical characterizations. Many alleged poisonings and other incidents, such as her daughter's premature death, may have rational explanations that have been twisted by later opponents.

Quotes
The traditional Chinese historical view of Wu Zetian generally was mixed—admiring her for her abilities in governing the state, but vilifying her for her actions in seizing imperial power. Luo Binwang even wrote along these lines in a declaration during her lifetime, in support of Li Jingye's rebellion. Typical was a commentary by the Later Jin dynasty historian Liu Xu, the lead editor of the Old Book of Tang:

"The year that Lady Wu declared herself regent, heroic individuals were all mournful of the unfortunate turn of events, worried that the dynasty would fall, and concerned that they could not repay the grace of the deceased emperor [i.e., Emperor Gaozong] and protect his sons. Soon thereafter, great accusations arose, and many innocent people were falsely accused and stuck their necks out in waiting for execution. Heaven and earth became like a huge cage, and even if one could escape it, where could he go? That was lamentable. In the past, the trick of covering the nose surprised the realm in its poisonousness, and the disaster of the human pig caused the entire state to mourn. In order to take over as empress, Empress Wu strangled her own infant daughter; her willingness to crush her own flesh and blood showed how great her viciousness and vile nature was, although this is nothing more than what jealous individuals and evil women might do. However, she accepted the words of righteousness and honored the upright. Although she was like a hen that crowed, she eventually returned the rightful rule to her son. She quickly dispelled the accusation against Wei Yuanzhong, comforted Di Renjie with kind words, respected the will of the times and suppressed her favorites, and listened to honest words and ended the terror of the secret police officials. This was good, this was good."

Some of the diversity in terms of points of agreement and even outright divergences in modern evaluations of Wu can be seen in the following quotes by modern non-Chinese authors:

"Wu Zetian (690–705) was an extraordinary woman, attractive, exceptionally gifted, politically astute and an excellent judge of men. With single minded determination, she overcame the opposition of the Confucian establishment through her own efforts, unique among palace women by not using her own family. Her rise to power was steeped in blood."

"'To the horror of traditional Chinese historians, all members of the shih class, the continued success of the T'ang was in large measure due to an ex-concubine who finally usurped the throne itself....Though she was ruthless towards her enemies, the period of her ascendency was a good one for China. Government was sound, no rebellions occurred, abuses in the army and administration were stamped out and Korea was annexed, an achievement no previous Chinese had ever managed.'"

"'China's only woman ruler, Empress Wu was a remarkably skilled and able politician, but her murderous and illicit methods of maintaining power gave her a bad reputation among male bureaucrats. It also fostered overstaffing and many kinds of corruption.'"

Confucian viewpoints
Wu Zetian's rise and reign was criticized harshly by Confucian historians like Liu Xu and Yuan Shu, But, some of those had praises for Wu Zetian like Liu Xu (in Quotes section), Sima Guang

In the early period of the Tang dynasty, because all the emperors were her direct descendants, Wu was evaluated favorably. But commentary in subsequent periods, especially the book Zizhi Tongjian compiled by Sima Guang, harshly criticized her. By the period of Southern Song dynasty, when Neo-Confucianism was firmly established as China's mainstream political ideology, it determined the evaluation of Wu.

Chancellors during reign
Wu Zetian had many chancellors during her reign as monarch of her self-proclaimed Zhou dynasty, many of them notable in their own right. (For full list see List of chancellors of Wu Zetian).

Television

 * Portrayed by Petrina Fung in the 1984 Hong-Kong TV series Empress Wu.
 * Portrayed by Angela Pan in the 1985 Taiwanese TV series The Empress of the Dynasty.
 * Portrayed by Liu Xiaoqing in the 1995 Chinese TV series Wu Zetian, in the 2007 TV series The Shadow of Empress Wu and in the 2011 TV series Secret History of Empress Wu.
 * Portrayed by Gua Ah-leh in the 2000 Chinese TV series Palace of Desire.
 * Portrayed by Qin Lan in the 2001 Chinese TV series Love Legend of the Tang Dynasty.
 * Portrayed by Alyssa Chia in the 2003 Chinese TV series Lady Wu: The First Empress.
 * Portrayed by Lü Zhong in the 2004 Chinese TV series Amazing Detective Di Renjie and its sequels Amazing Detective Di Renjie 2, Amazing Detective Di Renjie 3 and Mad Detective Di Renjie.
 * Portrayed by Siqin Gaowa in the 2006 Chinese TV series Wu Zi Bei Ge.
 * Portrayed by Yang Geum-seok in 2006–2007 KBS TV series Dae Jo Yeong.
 * Portrayed by Rebecca Chan in the 2009 Chinese TV series The Greatness of a Hero.
 * Portrayed by Yin Tao, Liu Xiaoqing and Siqin Gaowa in the 2011 Chinese TV series Secret History of Empress Wu.
 * Portrayed by Wang Li Ke in the 2011 Chinese TV series Meng Hui Tang Chao.
 * Portrayed by Kara Hui in the 2011 Chinese TV series Women of the Tang Dynasty and in the 2015 TV series Heroes of Sui and Tang Dynasties 5.
 * Portrayed by Zhang Ting in the 2011 Chinese TV series Beauty World.
 * Portrayed by Liu Yuxin in the 2012 Chinese TV series Secret History of Princess Taiping.
 * Portrayed by Fan Bingbing in the 2014 Chinese TV series The Empress of China.
 * Portrayed by Sheren Tang in the 2014 Chinese TV series Cosmetology High.
 * Portrayed by Ruby Lin in the 2014 Chinese TV series Young Sherlock.
 * Portrayed by Sophie Wu in the 2015 episode of Horrible Histories.
 * Portrayed by Jiao Junyan in the 2017 Chinese TV series Legendary Di Renjie.
 * Portrayed by Yong Mei in the 2021 Chinese TV series Luoyang.

Films

 * Portrayed by Gu Lanjun in the 1939 Chinese movie The Empress Wu Tse-tien.
 * Portrayed by Li Lihua in the 1963 Hong-Kong movie Empress Wu Tse-Tien.
 * Portrayed by Carina Lau in the 2010 Chinese-Hong Kong movie Detective Dee and the Mystery of the Phantom Flame, its prequels Young Detective Dee: Rise of the Sea Dragon in 2013 and Detective Dee: The Four Heavenly Kings in 2018.

Video games

 * Wu appears in the mobile game Fate/Grand Order as an Assassin class servant.
 * Wu appears in the turn-based strategy games Civilization II, Civilization V and Civilization VI as a leader of the Chinese civilization.
 * Wu appears as a character in the mobile game Law of Creation as a front-row tank.
 * Wu appears as a minister earned in the mobile game Call Me Emperor after getting first place in the cross server intimacy event.
 * Wu appears in the mobile game Rise Of Kingdoms as a legendary Chinese civilization Commander.
 * Wu appears as the highest-paying symbol in Wu Zetian, a slot machine published by Realtime Gaming
 * Wu appears as a Fabled Support Hero in the mobile game Royal Chaos

Novels

 * Wu is the protagonist, known as Mei, of the historically inspired fiction novel Moon in the Palace and its sequel The Empress of Bright Moon, both by Weina Dai Randel. Both are retellings of her life leading up to becoming Empress Wu.
 * Xiran Jay Zhao's debut novel, Iron Widow, is a reimagining of Wu's life.
 * Wu is the protagonist and narrator of Shan Sa's historical novel  Impératrice , published in France in 2003. The novel, translated by Adriana Hunter, was published in English as Empress in 2006.

title: Wu Zetian


text:
Pulse-position modulation

Pulse-position modulation (PPM) is a form of signal modulation in which M message bits are encoded by transmitting a single pulse in one of $$2^M$$ possible required time shifts. This is repeated every T seconds, such that the transmitted bit rate is $$M/T$$ bits per second. It is primarily useful for optical communications systems, which tend to have little or no multipath interference.

History
An ancient use of pulse-position modulation was the Greek hydraulic semaphore system invented by Aeneas Stymphalus around 350 B.C. that used the water clock principle to time signals. In this system, the draining of water acts as the timing device, and torches are used to signal the pulses. The system used identical water-filled containers whose drain could be turned on and off, and a float with a rod marked with various predetermined codes that represented military messages. The operators would place the containers on hills so they could be seen from each other at a distance. To send a message, the operators would use torches to signal the beginning and ending of the draining of the water, and the marking on the rod attached to the float would indicate the message.

In modern times, pulse-position modulation has origins in telegraph time-division multiplexing, which dates back to 1853, and evolved alongside pulse-code modulation and pulse-width modulation. In the early 1960s, Don Mathers and Doug Spreng of NASA invented pulse-position modulation used in radio-control (R/C) systems. PPM is currently being used in fiber-optic communications, deep-space communications, and continues to be used in R/C systems.

Synchronization
One of the key difficulties of implementing this technique is that the receiver must be properly synchronized to align the local clock with the beginning of each symbol. Therefore, it is often implemented differentially as differential pulse-position modulation, whereby each pulse position is encoded relative to the previous, such that the receiver must only measure the difference in the arrival time of successive pulses. It is possible to limit the propagation of errors to adjacent symbols, so that an error in measuring the differential delay of one pulse will affect only two symbols, instead of affecting all successive measurements.

Sensitivity to multipath interference
Aside from the issues regarding receiver synchronization, the key disadvantage of PPM is that it is inherently sensitive to multipath interference that arises in channels with frequency-selective fading, whereby the receiver's signal contains one or more echoes of each transmitted pulse. Since the information is encoded in the time of arrival (either differentially, or relative to a common clock), the presence of one or more echoes can make it extremely difficult, if not impossible, to accurately determine the correct pulse position corresponding to the transmitted pulse. Multipath in Pulse Position Modulation systems can be easily mitigated by using the same techniques that are used in Radar systems that rely totally on synchronization and time of arrival of the received pulse to obtain their range position in the presence of echoes.

Non-coherent detection
One of the principal advantages of PPM is that it is an M-ary modulation technique that can be implemented non-coherently, such that the receiver does not need to use a phase-locked loop (PLL) to track the phase of the carrier. This makes it a suitable candidate for optical communications systems, where coherent phase modulation and detection are difficult and extremely expensive. The only other common M-ary non-coherent modulation technique is M-ary frequency-shift keying (M-FSK), which is the frequency-domain dual to PPM.

PPM vs. M-FSK
PPM and M-FSK systems with the same bandwidth, average power, and transmission rate of M/T bits per second have identical performance in an additive white Gaussian noise (AWGN) channel. However, their performance differs greatly when comparing frequency-selective and frequency-flat fading channels. Whereas frequency-selective fading produces echoes that are highly disruptive for any of the M time-shifts used to encode PPM data, it selectively disrupts only some of the M possible frequency-shifts used to encode data for M-FSK. On the other hand, frequency-flat fading is more disruptive for M-FSK than PPM, as all M of the possible frequency-shifts are impaired by fading, while the short duration of the PPM pulse means that only a few of the M time-shifts are heavily impaired by fading.

Optical communications systems tend to have weak multipath distortions, and PPM is a viable modulation scheme in many such applications.

Applications for RF communications
Narrowband RF (radio frequency) channels with low power and long wavelengths (i.e., low frequency) are affected primarily by flat fading, and PPM is better suited than M-FSK to be used in these scenarios. One common application with these channel characteristics, first used in the early 1960s with top-end HF (as low as 27 MHz) frequencies into the low-end VHF band frequencies (30 MHz to 75 MHz for RC use depending on location), is the radio control of model aircraft, boats and cars, originally known as "digital proportional" radio control. PPM is employed in these systems, with the position of each pulse representing the angular position of an analogue control on the transmitter, or possible states of a binary switch. The number of pulses per frame gives the number of controllable channels available. The advantage of using PPM for this type of application is that the electronics required to decode the signal are extremely simple, which leads to small, light-weight receiver/decoder units (model aircraft require parts that are as lightweight as possible). Servos made for model radio control include some of the electronics required to convert the pulse to the motor position – the receiver is required to first extract the information from the received radio signal through its intermediate frequency section, then demultiplex the separate channels from the serial stream, and feed the control pulses to each servo.

PPM encoding for radio control
A complete PPM frame is about 22.5 ms (can vary between implementation), and signal low state is always 0.3 ms. It begins with a start frame (high state for more than 2 ms). Each channel (up to 8) is encoded by the time of the high state plus the lower state. (PPM high state + 0.3 = servo PWM pulse width).

More sophisticated radio control systems are now often based on pulse-code modulation, which is more complex but offers greater flexibility and reliability. The advent of 2.4 GHz band FHSS radio-control systems in the early 21st century changed this further.

Pulse-position modulation is also used for communication with the ISO/IEC 15693 contactless smart card, as well as in the HF implementation of the Electronic Product Code (EPC) Class 1 protocol for RFID tags.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Pulse-position modulation