In 581 AD, Yang Jian accepted the abdication of Emperor Jing of Northern Zhou, ascended the throne, established the Great Sui dynasty, and changed the era name to Kaihuang. Yang Jian was Emperor Wen of Sui.
Shortly after Yang Jian ascended the throne, the Turks, claiming to be the brotherly state of the Northern Zhou, used the pretext of avenging the Northern Zhou to breach the Great Wall, launching raids of burning, killing, and looting. In reality, the Turks were driven to plunder the Central Plains because a famine on the northern Mongolian steppes made survival impossible. Before the establishment of the Sui Dynasty, the Northern Zhou had maintained friendly relations with the Turks, paying them annual tribute. After Yang Jian founded the Sui Dynasty, he neither offered tribute nor provided aid to the struggling Turks, which enraged Shabolüe Khan, prompting him to order Turkish cavalry to invade the border and commit atrocities.
After receiving the news, Yang Jian immediately mobilized troops and deployed generals to resist the harassment of Turkic cavalry. However, the Sui army fought many battles against the Turkic cavalry, winning few and losing many. Yang Jian was planning to annex the Chen Dynasty, and if he could not completely conquer the Turks, his grand plan to annex the Chen Dynasty would inevitably be affected.
Just as Yang Jian was troubled by this, a Northern Zhou general named Zhangsun Sheng appeared. Zhangsun Sheng had once escorted a Northern Zhou princess to the Turks for a marriage alliance and lived in Turkic territory for a year. During that year, he befriended many Turkic nobles. The Turkic Shabolüe Khan had a highly respected and cunning younger brother named Chuluohou. Shabolüe Khan, jealous of talent and ability, constantly feared that his brother would pose a threat to him. Upon learning this, Chuluohou sought Zhangsun Sheng's help, hoping to use the Sui Dynasty's power to deal with his brother. When Zhangsun Sheng met Yang Jian, he proposed a strategy of exploiting the conflicts among the Turkic tribes, supporting the weaker tribes to counter the stronger ones. Yang Jian found this approach feasible and decided to follow Zhangsun Sheng's plan to deal with the Turks.
Afterwards, Yang Jian sent envoys to the Western Regions to forge ties with Tardu Qaghan of the Turkic tribes there. To sow discord among the Turkic tribes, Yang Jian deliberately bestowed upon Tardu Qaghan a wolf-head banner and other gifts. When Shabolüe Qaghan learned of this, he indeed grew suspicious of Tardu Qaghan. Yang Jian also dispatched Zhangsun Sheng with large amounts of gold, silver, and jewels to build relations with tribes such as the Khitans and the Xi. Zhangsun Sheng also met with Chuluohou to stir up his relationship with Shabolüe Qaghan, hoping he would side with the Sui Dynasty.
Shabolüe Khan was gradually isolated. Furious, he planned to lead a large army to teach the Sui Dynasty a lesson. At this moment, Zhangsun Sheng spread a rumor that the Tiele tribes, who had submitted to the Turks, had launched an attack on the Turkic khan's headquarters. Shabolüe Khan believed this without hesitation and quickly led his army back to the northern steppes.
In 583 AD, Yang Jian, seeing that the time was ripe, issued orders for a counterattack against the Turks. Tens of thousands of Sui Dynasty troops advanced in eight columns toward the northern deserts. The main forces of both sides clashed at Baidao River (present-day northwest of Hohhot, Inner Mongolia). Shabolüe Khan held the advantage of terrain, believing the Sui army was too weak to dare attack the Turkish forces. However, the Sui army quickly made him pay for his underestimation. The Sui main force launched a fierce assault on the Turkish camp, routing the Turkish army completely. Subsequently, the Sui army pursued its advantage, defeating the khans of various Turkish tribes one after another, achieving a major victory in the war against the Turks. The Turkish tribes gradually declined and could no longer pose a threat to the Sui Dynasty.
After that, Yang Jian implemented a series of political and economic reforms, steadily strengthening the Sui Dynasty's national power.
After the Sui Dynasty was established, Yang Jian discovered that the local official system suffered from chaotic organization and an overstaffed bureaucracy. At that time, some areas with only a few hundred households were governed by two commanderies; some regions less than a hundred li in length had several counties set up; and some counties had merely three or four households. Many young people entering officialdom were at a loss when faced with the numerous administrative divisions and official titles, often needing a long time to become familiar with them.
Faced with such a chaotic situation, Yang Jian did not retreat. He established the principle of "retain the essential, eliminate the idle, and merge the small into the large," and began a large-scale reorganization of the local official system.
First, Yang Jian abolished the commandery system, changing the long-standing three-tier system of provinces, commanderies, and counties from the previous dynasty into a two-tier system of provinces and counties, where counties were directly under the jurisdiction of provinces. Later, Yang Jian changed provinces back to commanderies, forming a two-tier system of commanderies and counties.
Secondly, Yang Jian created many systems to prevent local officials from gaining excessive power or engaging in corruption and lawlessness. For example, he stipulated that local officials could serve a term of only three years and had to leave office afterward; he required officials to serve in places other than their hometowns, forbidding them from holding office in their home prefectures or counties; and he prohibited officials from holding the same position twice in the same locality.
Third, the system that had been in place since the Han Dynasty, allowing local officials to independently select their subordinates, was abolished. Before the Sui Dynasty, local officials had the right to appoint their own staff, which easily led to master-servant relationships and the emergence of regional separatist forces, undermining the central government's control. Yang Jian abolished this system and placed the power to appoint and evaluate local officials under the Ministry of Personnel, ensuring that all levels of local government could only answer to the central authority.
Fourth, Yang Jian also mandated that local governors or their deputies report to the capital annually at year-end, thereby strengthening control over local officials.
In addition to reforming local official systems, Yang Jian established the Three Departments and Six Ministries system at the central level, strengthening imperial power.
Thanks to Yang Jian's efforts, within twenty years of its founding, the Sui Dynasty experienced a period of peace and prosperity where the people lived stable and contented lives. This era came to be known as the "Kaihuang Golden Age."