The Sui and Tang dynasties followed the political system of the Southern and Northern Dynasties, and the lack of imperial power was a common problem of all dynasties. With the collapse of imperial power and the localities, the national power cannot be fully integrated. In this situation, unless you encounter a male lord, you can control the various forces in the country and make the country strong. But this human-based magnanimity is accompanied by contingencies, and once the new emperor is unable to unite the majority without leadership charisma, which is a very easy situation under the imperial hereditary system, the local power will resurrect, and the imperial power will be suspended, and even the emperor's abolition will be in the hands of these people.
The problem encountered by Emperor Gaozong of Tang was that the Guanlong aristocratic clique was powerful, and as emperor, he could only be a rubber stamp-like puppet. Emperor Gaozong of Tang used the establishment of Wu Zetian as empress to divide and disintegrate the Guanlong military clique and achieve centralized power. Later, Emperor Gaozong fell ill, and Wu Zetian, as a political ally of Emperor Gaozong, was put on the forefront and became the ruler of the Tang Empire.
Wu Zetian vigorously promoted the Han men and developed the imperial examination system, which seriously affected the interests of the family clan, and they held up groups to carry out explicit or covert resistance, and even launched war. In order to control the development of the situation, Wu Zetian could only appoint cool officials and adopt severe punishment laws to purge dissident forces in the country. Such a toss-up killed a large number of famous generals who could fight in battle, resulting in a significant decline in the combat effectiveness of the Tang army.
At the same time, because the Tang Dynasty reached the most extensive territory during the reign of Emperor Gaozong, the Tang Emperor's military system of competing with the masses in Guanzhong gradually collapsed, partly because the Juntian system was destroyed, but also because the geographical scope of conquest was too wide, and the imperial court needed more professional troops to carry out combat tasks. Therefore, the prefectural military system, which lacked economic foundation, ability, and willingness, was already facing a collapse situation during the time of Emperor Gaozong, and many good families were reluctant to go on the expedition, and even spent money to let others go on their own. It is said that "good iron does not strike nails, and good men do not use soldiers" came from that time.
Li Zhi
After being met with the soft resistance of the family clan, Wu Zetian seemed to be full of talents in the middle of the dynasty, but there were not many people who could be used when they actually went to war. The success rate of the Han Men Shizi that Wu Zetian had high hopes for was too low to completely replace the talent team of the Family Clan. In the era when movable type printing was not widespread, the high cost of learning made it difficult for ordinary people to study. The bureaucracy of the imperial court was filled with those who had intricate relations with the family clan.
Therefore, before and after Wu Zetian became emperor, she actually had no way to mobilize all the energy of the empire to fight a foreign war, and even she had to deliberately limit her desire for such a foreign war. Because foreign wars can shape prestige, but at the same time they can be exploited by careerists, thus creating a greater political crisis. The female of Wu Zetian's ruling process is the emperor, and the political model of centralized power needs time to transition, and stability must be greater than everything.
Therefore, whether it is objective factual or subjective will, Wu Zetian has chosen a pragmatic attitude at this time to avoid foreign war. Even so, the Wu Zetian period basically maintained the territory and status of the Tang Dynasty. In the later period of Wu Zetian's reign, with the gradual consolidation of his rule, the combat effectiveness of the Tang army was improved, and its inferiority on the battlefield was reversed. Later, on the basis of the military experience of the Wu Zetian Dynasty, the Tang Dynasty developed a system of moderation and once again achieved the suppression of the armed forces of the surrounding ethnic groups.
Pei Xingjian
In the northwest, the Tang Dynasty and Tubo were constantly fighting for the smoke of the western region, and the four towns of Anxi were put at a standstill, and Emperor Gaozong used Pei Xingjian to pass through the western region and reset the four towns in the first year of The Lu Dynasty (679). In the third year of the Arch (687), while Empress Wu was busy usurping the throne, Tubo occupied the four towns of Anxi, and its forwards reached Dunhuang. In the first year of Empress Wu's reign (692), Wu Zetian sent Wang Xiaojie to lead an army to retake the four towns of Anxi and send troops to stay permanently, thus ending the situation of Tang Fan's repeated battles in the western region.
In the north, the Eastern Turks had been destroyed during the reign of Emperor Taizong of Tang, and the Turks were revived during the reign of Emperor Gaozong of Tang. In October of the first year of the reign of Emperor Zhonglu (679), the Turkic chieftain Ashwin Fu and Feng Zhili, a subordinate of the Capital Protectorate, rebelled against the Tang Dynasty, and war broke out against the Tang Dynasty, with both sides winning and losing each other. Before Wu Zetian claimed the throne, cheng Wuting, a general who fought against the Turks, was killed by Wu Zetian for defending Pei Yan, and the Turkic invasion became more rampant. During the reign of Wu Zetian, military towns were set up outside the Yellow River to drive the Turkic forces out of the southern desert region. During the reign of Emperor Xuanzong of Tang, he took advantage of the Turkic infighting and united with the Hui to destroy the Later Turkic Khaganate.
Wu Shuo
In the northeast, during the Wu Zetian period, the Khitan rose, and in the first year of the Banzai Tongtian Dynasty (696), due to the tyranny of Zhao Wenqi, the governor of Yingzhou, the Khitan governor of Songmo, Li Duzhong, and the old chengzhou assassin ShiSun Wanrong rebelled against The Zhou and attacked the Hebei region. Wu Zetian sent troops to fight three times, lost troops, lost many battles, and finally completely pacified the northeast region with the help of Xi and the Turks. The rise of the Khitans was thus delayed for more than 200 years.
In the second year of Chang'an (702), Wu Zetian placed the Beiting Capital Protectorate in Tingzhou (present-day Jimsar, Xinjiang), replacing the Jinshan Du Protectorate and administering the Western Turk homeland, still subordinate to the Anxi Capital Protectorate, once again consolidating the jurisdiction of the Tang Dynasty central government over the Western Regions.
In summary, the foreign military of the Wuzhou Empire is actually the result of the adjustment of domestic and foreign policies since the founding of the Tang Dynasty, and no matter what the result is, it is not objective enough to blame all this on Wu Zetian's rule.