Sui dynasty
The Sui dynasty was a Chinese imperial dynasty that ruled from 581 to 618 AD. The re-unification of China proper under the Sui brought the Northern and Southern dynasties era to a close, ending a prolonged period of political division since the War of the Eight Princes. The Sui endeavoured to rebuild the state, re-establishing and reforming many imperial institutions; in so doing, the Sui laid much of the foundation for the subsequent Tang dynasty, which after toppling the Sui would ultimately preside over a new golden age in Chinese history. Often compared to the Qin dynasty, the Sui likewise unified China after a prolonged period of division, undertook wide-ranging reforms and construction projects to consolidate state power, and collapsed after a brief period.
The dynasty was founded by Yang Jian, who had been a member of the military aristocracy that had developed in the northwest during the prolonged period of division. The Sui capital was initially based in Daxing, but later moved to Luoyang in 605 AD, which had been re-founded as a planned city. Wen and his successor Emperor Yang undertook various centralising reforms, most notably among them the equal-field system that aimed to reduce economic inequality and improve agricultural productivity, the system, which preceded the Three Departments and Six Ministries system, and the standardisation and re-unification of the coinage. The Sui also encouraged the spread of Buddhism throughout the empire. By the dynasty's mid-point, the state experienced considerable prosperity, enjoying a vast agricultural surplus that supported rapid population growth.
The Sui engaged in many construction mega-projects, including the Grand Canal, the extension of the Great Wall, and the reconstruction of Luoyang. The canal linked Luoyang in the east with Chang'an in the west, with the eastern economic and agricultural centres towards Jiangdu and Yuhang, and with the northern frontiers. While the initial motivations of the canal were improving grain shipments to the capital and military logistics—including the transportation of troops—the new, reliable inland route would ultimately facilitate domestic trade, the flow of people, and cultural exchange for centuries. These mega-projects were led by an efficient centralised bureaucracy, but forcibly conscripted millions of workers at a heavy human cost.
After a series of military campaigns against the Goguryeo in the Korean peninsula, which had ended in defeat by 614 AD, the dynasty disintegrated amid popular revolts that culminated in the assassination of Emperor Yang by a minister named Yuwen Huaji in 618 AD. The dynasty, which lasted for only 37 years, was undermined by ambitious wars and construction projects, which overstretched its resources. Particularly, under Emperor Yang, heavy taxation and compulsory labour duties would eventually induce widespread revolts and brief civil war following the fall of the dynasty.
History
Foundation and Emperor Wen
During the late Northern and Southern dynasties period, the Xianbei-led Northern Zhou conquered the Northern Qi in 577, reunifying northern China. By this time, Yang Jian, a Northern Zhou general who would later found the Sui dynasty, became the regent to the Northern Zhou court. Yang Jian's clan, the Yang clan of Hongnong, had Han origins and claimed descent from the Han dynasty general Yang Zhen, but had intermarried with the Xianbei for generations. Yang Jian's daughter was the Empress Dowager, and her stepson, Emperor Jing of Northern Zhou, was a child. After crushing an army in the eastern provinces, Yang Jian usurped the throne from the Northern Zhou rulers, and became Emperor Wen of Sui. While formerly the Duke of Sui when serving at the Zhou court, where the character literally means 'to follow', implying loyalty, Emperor Wen created a unique character, morphed from that in his former title, as the name of his new dynasty. In a bloody purge, Wen had 59 Zhou princes eliminated, in contrast to his later reputation as the "Cultured Emperor". Emperor Wen emphasised Han cultural identity during his reign, abolishing the anti-Han policies of Northern Zhou and reclaiming his Han surname of Yang. Having won the support of Confucian scholars who held power in previous Han dynasties, Emperor Wen initiated a series of reforms aimed at strengthening his empire for the wars that would reunify China.In his campaign for southern conquest, Emperor Wen assembled thousands of boats to confront the naval forces of the Chen dynasty on the Yangtze. The largest of these ships were very tall, having five layered decks and the capacity for 800 non-crew personnel. They were outfitted with six 50-foot-long booms that were used to swing and damage enemy ships, or to pin them down so that Sui marine troops could use act-and-board techniques. Besides employing Xianbei and other Chinese ethnic groups for the fight against Chen, Emperor Wen also employed the service of people from southeastern Sichuan, which Sui had recently conquered.
In 588, the Sui had amassed 518,000 troops along the northern bank of the Yangtze River, stretching from Sichuan to the East China Sea. The Chen dynasty could not withstand such an assault. By 589, Sui troops entered Jiankang and the last emperor of Chen surrendered. The city was razed to the ground, while Sui troops escorted Chen nobles back north, where the northern aristocrats became fascinated with everything the south had to provide culturally and intellectually.
Although Emperor Wen was famous for bankrupting the state treasury with warfare and construction projects, he made many improvements to infrastructure during his early reign. He established granaries as sources of food and as a means to regulate market prices from the taxation of crops, much like the earlier Han dynasty. The large agricultural surplus supported rapid growth of population to a historical peak, which was only surpassed during the reign of Emperor Xuanzong of Tang more than a century later.
The capital of Daxing, while situated in the militarily secure heartland of Guanzhong, was remote from the economic centres to the east and south of the empire. Emperor Wen initiated the construction of the Grand Canal, with completion of the first route that directly linked Chang'an to the Yellow River. Later, Emperor Yang enormously enlarged the scale of the Grand Canal construction.
Externally, the emerging Turkic Khaganate in the north posed a major threat to the newly founded dynasty. With Emperor Wen's diplomatic manoeuvre, the Khaganate split into Eastern and Western halves. Later the Great Wall was consolidated to further secure the northern territory. In Emperor Wen's late years, the first war with Goguryeo, ended with defeat. Nevertheless, the celebrated "Reign of Kaihuang" was considered by historians as one of the apexes in the two millennium imperial period of Chinese history.
The Sui emperors were from the northwest military aristocracy, and they cited the Han clan as their ancestors. They emphasised their Han ancestry, and claimed descent from the Han official Yang Zhen. The New Book of Tang traces their patrilineal ancestry to the Zhou dynasty kings via the Dukes of Jin. The Li of Zhaojun and the Lu of Fanyang hailed from Shandong and were related to the Liu clan, which was also linked to the Hongnong Yangshi of and other clans of Guanlong.
File:Yu Hong Tomb general view.jpg|thumb|Tomb of Yu Hong, a Sogdian merchant buried in Taiyuan in 592. Shanxi Museum.
The Yang of Hongnong, Jia of Hedong, Xiang of Henei, and Wang of Taiyuan from the Tang dynasty were later claimed as ancestors by Song dynasty lineages.
Information about these major political events in China were somehow filtered west and reached the Byzantine Empire, the continuation of the Roman Empire in the east. From Turkic peoples of Central Asia the Eastern Romans derived a new name for China after the older Sinae and Serica: Taugast, during its Northern Wei period. The 7th-century Byzantine historian Theophylact Simocatta wrote a generally accurate depiction of the reunification of China by Emperor Wen of the Sui dynasty, with the conquest of the rival Chen dynasty in southern China. Simocatta correctly placed these events within the reign period of Byzantine ruler Maurice. Simocatta also provided cursory information about the geography of China, its division by the Yangzi River and its capital Khubdan along with its customs and culture, deeming its people "idolatrous" but wise in governance. He noted that the ruler was named "Taisson", which he claimed meant "Son of God", perhaps Chinese Tianzi or even the name of the contemporary ruler Emperor Taizong of Tang.
Emperor Yang and re-conquest of Vietnam
ascended the throne after his father's death, possibly by murder. He further extended the empire, but unlike his father, did not seek to gain support from the nomads. Instead, he restored Confucian education and the Confucian examination system for bureaucrats. By supporting educational reforms, he lost the support of the nomads. He also started many expensive construction projects such as the Grand Canal, and became embroiled in several costly wars. Between these policies, invasions into China from Turkic nomads, and his growing life of decadent luxury at the expense of the peasantry, he lost public support and was eventually assassinated by his own ministers.Both Emperors Yang and Wen sent military expeditions into Vietnam as Annam in northern Vietnam had been incorporated into the Chinese empire over 600 years earlier during the Han dynasty. However the Kingdom of Champa in central Vietnam became a major counterpart to Chinese invasions to its north. According to Ebrey, Walthall, and Palais, these invasions became known as the Linyi-Champa Campaign.
The Hanoi area formerly held by the Han and Jin dynasties was easily retaken from the Early Lý dynasty ruler Lý Phật Tử in 602. A few years later the Sui army pushed farther south and was attacked by troops on war elephants from Champa in southern Vietnam. The Sui army feigned retreat and dug pits to trap the elephants, lured the Champan troops to attack then used crossbows against the elephants causing them to turn around and trample their own soldiers. Although Sui troops were victorious many succumbed to disease as northern soldiers did not have immunity to tropical diseases such as malaria.