When the Northern Zhou Dynasty defeated the Northern Qi Dynasty in 577 CE, this was the culminating moment and ultimate advantage for the northern Chinese to face south. The southern dynasties had lost hope in conquering the north, and the situation of conquest from north-to-south was only delayed in 523 with civil war. The Sui Dynasty began when Emperor Wen's daughter became the Empress Dowager of Northern Zhou, with her stepson as the new emperor. After crushing an army disused in the eastern provinces as the prime minister of Zhou, Emperor Wen took the throne by force and proclaimed himself emperor. In a bloody purge, he had fifty-nine princes of the Zhou royal family eliminated yet nevertheless became known as the 'Cultured Emperor' (581 - 604 CE). Emperor Wen abolished the anti-Han policies of Zhou and reclaimed his Han surname of Yang. Having won the support of Confucian scholars who had powered previous Han dynasties (abandoning the nepotism and corruption of the nine-rank system), 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 River. The largest of these ships were very tall, having five layered decks and the capacity for 800 passengers. 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 aborigines from southeastern Sichuan, a people that Sui had recently conquered.
In 588 CE, the Sui had amassed 518,000 troops along the northern bank of the Yangtze River, stretching from Sichuan to the Pacific Ocean. Meanwhile, the Chen Dynasty was collapsing and could not withstand such an assault. By 589 CE, Sui troops entered Jiankang (Nanjing) and the last emperor of the southern Chen dynasty 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.
Emperor Yang of Sui gained the throne after his father's death, possibly by murder. He further extended the empire but unlike his father he 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 of China, 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 Wen and Yang 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 (202 BC - 220 CE). However the ancient Kingdom of Champa in southern 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 (602-605 CE).
The Hanoi area formerly held by the Han and Jin dynasties was easily recovered from the local ruler 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. The biggest factor that led to the downfall of Sui Dynasty was a series of massive expeditions into the Korean Peninsula to invade Goguryeo, one of the Three Kingdoms of Korea. The Sui Dynasty's second emperor, Emperor Yang conscripted many soldiers for the campaign. This army was so enormous it recorded in historical texts that it took 30 days for all the armies to exit their last rallying point near Shanhaiguan before invading Korea. In one instance the soldiers—both conscripted and paid—listed over 3000 warships, up to 1.15 million infantry, 50,000 cavalry, 5000 artillery, and more. There were as many supporting laborers and an exorbitant military budget that included mounds of equipment and rations (most of which never reached the Chinese vanguard, as they were captured by Goguryeo armies already). The army stretched to 1000 li or about 410 kilometers across rivers and valleys, over mountains and hills.
In all four main campaigns, the military conquest ended in failure. Many Sui soldiers were defeated by the prominent army leader Eulji Mundeok of Goguryeo - in prominent battles such as The Battle of Salsu River. According to the Book of Tang, of the 305,000 Chinese troops, only 2,700 returned to China (although the Tang was known to have exaggerated the failures of their predecessors to justify their own rule). Eventually resentment of the emperor increased and the wars, coupled with revolts and assassinations, led to the fall of the Sui Dynasty. One great accomplishment was rebuilding the Great Wall of China, but this, along with other large projects, strained the economy and angered the resentful workforce employed. During the last few years of the Sui Dynasty, the rebellion that rose against it took many of China's able-bodied men from rural farms and other occupations, which in turn damaged the agricultural base and the economy further. Men would deliberately break their limbs in order to avoid military conscription, calling the practice "propitious paws" and "fortunate feet." In the year 642, Emperor Taizong of Tang made an effort to eradicate this practice by issuing a decree of a stiffer punishment for those who were found to deliberately injure and heal themselves.
Although the Sui Dynasty was relatively short (581-618 CE), much was accomplished during its tenure. The Grand Canal was one of the main accomplishments. It was extended north from the Hangzhou region across the Yangzi to Yangzhou and then northwest to the region of Luoyang. The eventual fall of the Sui dynasty was due to the many losses in Southern Manchuria and North Korea. It was after these defeats and losses that the country was left in ruins and rebels soon took control of the government. Emperor Yang was assassinated in 618. He had gone South after being defeated by Korea and was killed by his advisors. Meanwhile, in the North, aristocrat Li Yuan held an uprising after which he ended up ascending the throne to become Emperor Gaozu of Tang. This was the start of the Tang Dynasty, one of the most-noted dynasties in Chinese history.
Buddhism was popular during the Six Dynasties period that preceded the Sui dynasty, spreading from India through Kushan Afghanistan into China during the Late Han period. Buddhism gained prominence during the period when central political control was limited. Buddhism created a unifying cultural force that uplifted the people out of war and into the Sui Dynasty. In many ways, Buddhism was responsible for the rebirth of culture in China under the Sui Dynasty. Emperor Wen and his empress had converted to Buddhism to legitimize imperial authority over China and the conquest of Chen.
The emperor presented himself as a Cakravartin king, a Buddhist monarch who would use military force to defend the Buddhist faith. In the year 601 CE, Emperor Wen had relics of the Buddha distributed to temples throughout China, with edicts that expressed his goals, "all the people within the four seas may, without exception, develop enlightenment and together cultivate fortunate karma, bringing it to pass that present existences will lead to happy future lives, that the sustained creation of good causation will carry us one and all up to wondrous enlightenment". Ultimately, this act was an imitation of the ancient Mauryan Emperor Ashoka of India. Rulers of the Sui Dynasty :
| Posthumous Name (Shi Hao) | Birth Name | Period of Reign | Era Names (Nian Hao) and their according range of years |
| Wéndì | Yáng Jiān | 581 - 604 | Kāihuáng 581 - 600 Rénshòu 601 - 604 |
| Yángdì or Míngdì | Yáng Guǎng | 604 - 618 | Dàyè 605 - 618 |
| Gōngdì | Yáng Yòu | 617 - 618 | Yìníng 617 - 618 |
| Gōngdì | Yáng Tóng | 618 - 619 | Huángtài 618 - 619 |
