The Western Jin gained control of the Yangzte with the fleet it had of warships in 279. The Sui founder Yang Jain followed the path of the Jin building a fleet of ships on his own. The Sui of the northern region planned an attack on the southern Chen Empire. The preparations for the attack began in 587. Most of the boats were built in Yong’an on the Yangtze. The larger warships could transport up to 800 men. The smaller vessels called the Yellow Dragons carried up to 100 men. In the fall of 588 the Sui armies were in place on the north side of the Yangtze, and on the Han River. Yang Jain had 518,ooo men broken into eight divisions. Chen soldiers were estimated at 100,000 men. The fleet at Yong’an made the first offensive. Yang Su took his men downstream to find 100 Green Dragon class warships. Yang Su decided to attack the Chen fleet at night. The attack worked, and Yang Su, and his men continued to fight to advance downriver. Chen Huiji attempted to bring 30,ooo men along with a thousand ships down the Yangtze to stop the fall of Jainkang. Yang Su, son of Yang Jain commanded the Sui fleet on the Han River. The Sui forces on the Han River sailed to the Yangtze to stop Chen Huiji. Jainkang fell to the Sui. Yang Su let the Chen soldiers he captured go. The earlier empires of the Western Wei, and the northern Zhou made tens of thousands of southerners slaves. The Sui attempted to be fair and to use restraint to win over the people of the south. The Sui made it a point not to exploit the Chen people after the war. Yang Jain who was a major factor in the unification of China was brought up in a Buddhist temple. Yang Jain was from the Han region. He claimed to be the legitimate Han heir. He led the conquest into the south against the Chen. It were his accomplishments as a warrior the became his main claim to fame. Buddhists were not accepted under the rule of the northern Zhou. Under the his reign Buddhists were granted new freedom. Confucians are adament about ones elders or ancestors. Going through austerities or sacrifices is part of Confucian custom. The new emperor allow for the customs to be carried out.
The emperor brought about the law of avoidance to prevent an official from serving in their region of origin. The law of avoidance forced officials in power to branch out, and adapt to new locations. The concept was to expand the Sui influence in the new unified China. The integration of officials into the various main regions of China contributed to the cause.
Following Yang Jain was his second son who became know as the Yang-ti emperor. Yang-ti took over for his father in 604. Under the rule of Yang-ti a series of canals were built continuing the progression of China. The Sui conquest left China divided. The Buddhist monks were well respected in southern China under the rule of the Chen. Emperor Yang-ti made an effort to make peace with the southern monks. Yang-ti built new temples for the Buddhist in Chiang-tu. The emperor also ordered Buddhist scriptures to be copied into books for the new temples to prevent them from getting lost. Yang-ti built Toaist temples in his southern Capital as well. The emperor invited Confucian intellects that served under the Chen to the temples to add to the perspective of the Buddhist or Taoist scholars. Yang-ti gave a large vegetarian feast for a thousand southern monks in Chiang-tu in 591. Chiang-tu became the most active place in southern China. It was in Chiang-tu where the most interactions of scholars in China took place.
At the time the Turks in the west were a threat as were the Koreans to the east. Koguryo Korea showed little respect for the empire. Sui advancement against Korea encountered all sorts of trouble in the Yellow Sea. Once the ships got to the capital the Korean forces fell back, then lured the Sui past the outer walls. A Koruryo force of men hid in a Buddhist temple then attacked the Sui soldiers driving them back to their ships. Korean commanders were able to lure the Sui force in. Sui forces were forced to fall back. Emperor Yang-ti insisted on regrouping his forces to go back to Korea again. The Sui attempted an all out assault failing on the next attack again. The Koreans were able to defend against all of the Sui moves. After the Sui fled the Koguryo followed them ambushing several thousand stragglers near the Liao River. The loss was the main reason for the fall of the Sui Empire.