The Southern and Northern Dynasties period ended with the reunification of China under Sui Wendi, a general from the north. His government, during his lifetime, was very stable, and he reformed the taxation system and worked on remarkable building projects. Sui Wendi, unlike previous Chinese rulers, adopted Buddhism, both as his own religion and as the official state religion, instead of the Confucian philosophy endorsed by previous rulers. However, much like the Qin Dynasty (to which it is often compared) the Sui only had one strong ruler; his son and successor, Sui Yangdi, lost the throne, which led to the start of the Tang Dynasty.
The Sui Dynasty was quite short, then, lasting from 580-618 CE. Its comparison to the Qin is fairly apt - for although the dynasty itself was short, it left many accomplishments for later rulers. The Sui Dynasty centralized and improved the administration of China greatly, building granaries to reduce the impact of famines, reinforcing the Great Wall, expanding the borders of China, and creating the Grand Canal to transport goods from the Yangtze River to Northern China.
The Sui encouraged merit-based government; civil servants were again given examinations, ending the privilege held by the nobility. The civil service system created by the Sui lasted until the end of the Dynastic system in 1911. The economy was also regulated; land was redistributed in a novel way: landlords were allowed to own land, but tenants were given parcels to farm (but not to sell), increasing agricultural productivity. The government also nationalized the minting of coins and standardized weights and measures. Taxes on the lower classes were reduced under Wen, promoting economic equality.
Buddhism, promoted by the government, blossomed during the Sui years. Rather than just a movement of the lower classes, Buddhism was a state-promoted theology, and China's philosophers advanced Buddhism as much as India's under the Sui. China also grew economically; trade was restarted with West Asia along the Silk Road, increasing China's prestige and forming the economic base that would lead China to thrive during the Tang years.
Emperor Yangdi, unfortunately, was not as skilled and able a governor as his father; he was given a flourishing, satisfied nation and abused the power it gave him. He overextended China's resources with the ambitious construction projects he mandated, and lived his own life in constant luxury. Taxes were raised drastically to support his extravagance, hurting the ordinary people. He fought wars repeatedly, most notably against Korea, which defeated China four times during this period. Rebellions began, and by 616 the situation was so frightening that Yangdi withdrew, hiding in Yangzhou city; in his absence, a general conquered the capital and when Yang was murdered two years later, this general, Liyuan, began the Tang Dynasty. | 
