In the Northern Song Dynasty, North Korea captured 280 Li of Liao and built 12 block.

In 986 AD, in order to recover, Song Taizong led an army to conquer Liao, which was called "Yongxi Northern Expedition" in history. The reason for the failure of the Northern Expedition was that Song underestimated the enemy's strength and the commander's actions were not coordinated. After the Song-Liao War, the Liao Dynasty launched three large-scale conquests against North Korea in order to force it to submit, mainly for the following reasons: First, North Korea was bordered by Khitan, but it broke off relations with it and turned to pay tribute to Song. And attempted to attack Liao country in Song Dynasty; The second is to accept a large number of Bohai immigrants and seize the opportunity to occupy the territory of the former Shanghai state; The third is to force North Korea to surrender to the Liao country and completely relieve the worries of the Liao country in running the Central Plains. Emperor Shengzong of Liao decided to March eastward to Korea. In 992, Liao appointed Xiao Hengde, who stayed in Tokyo, as the commander-in-chief, led 800,000 troops and launched the first large-scale conquest of Korea. North Korea was in a hurry, and the Liao army quickly attacked and occupied pengshan county. After the Liao army occupied pengshan county, Xiao Hengde, the head coach, wrote to the North Korean court to urge it to descend quickly. North Korea sent Li Mengkun to the camp to negotiate, and Xiao ordered North Korea to "get off quickly if you want peace" and "leave or die". The king of South Korea is hesitant about peace and war. Xiao Hengde led the army to continue south and headed for Rong 'an Town on the south bank of the Qinghe River, but it was strongly resisted by the North Korean army led by Da Dao Xiu and Geng Fang. Xiao Sui didn't dare to take any more risks, so he sent someone to promote surrender. North Korea then sent Xu Xi as a special envoy to Liao Ying to make peace. Xu Xi argued, so Emperor Sheng Zong of Liao sent Xiao Hengde back to Korea for peace and communication. Due to Xu Xi's outstanding diplomatic skills, although North Korea failed militarily, it won an unexpected victory in diplomacy. The two countries reached a peace agreement, and South Korea gained 280 miles of territory in Jiangdong. The pink part is the contents of the 280-nautical-mile territorial peace talks won by South Korea as follows: recently announced, but it has long been easy to communicate with other countries, and the territory is connected with the soil. Although it is a small matter, there are rules and regulations, and it will take a long time. If it is not set in preparation, it will hinder people. Therefore, I discussed with other countries to let those who want to seize the road to build a city find out the exact fate and consider it for themselves. I plan to build five cities to the west of Yalu River, and I plan to start construction at Zhucheng in early March. Please ask the king to command in advance, from Anbei government soldiers to 280 miles east of Yalu River, step on the field, and consider the distance in the field to complete the city. Send a servant and start at the same time. Several cities were built together, and the early return trip, expensive transportation, chariots and horses, long-distance tribute, and always serving the imperial court, all came from Ye Ankang's plan. According to the provisions of the peace conditions reached with Xiao Xunning, one is to take Liao as the official crescent moon, use the Liao country number, and break diplomatic relations with Song. Second, Liao built five cities in the west with the Yalu River as the center, and started construction in March. Third, North Korea can build cities in the area 280 miles east of the Yalu River from Anbei government soldiers, but the number of cities to be built should be notified to Liao. Fourth, the time of building a city should be consistent with the Liao Dynasty. That year, Korea began to implement the title of the Khitan. In April of the same year, it sent a servant, Park Liangrou, to appear as a Khitan, and to tell the truth, to ask for prisoners. In June, Koryo sent Yuan Yuru to beg the Song Taishi to report the service of the year before last. In the north of Song Dynasty, it is better to be ashamed than to act rashly, but the gift is returned. "Song's move is China and South Korea, and it is natural to break up with Song. At this point, Korea and Qidan established a tribute relationship. Since then, South Korea has taken a series of measures to strengthen its relations with Liao and repair the negative effects of the war between the two countries. In August, 1994, "Qidan was sent to prostitution, but he gave up." In 995, Han gave Li the gift from Qidan, and then entered Eagle Country. In September of the same year, "Li Feng sent ten boys to learn their language in Qidan as a gift", and "Zhao of Zuo Chengxuan proposed to him in the name of Qidan, and promised to keep Xiao Huande, the daughter of Tokyo, as his wife". In view of its conquest of Korea, the Liao Dynasty forced North Korea to pay tribute. In order to win over North Korea, it "sent letters to Xiao, Yushi, Li Wan, etc." and sent special envoys to award Wang Zhi the title of korean king. According to the peace agreement reached between Li and Liao, North Korea owns 280 miles of land in the east of the river, so it set out to build a city to defend it. In 994, Koryo ordered Xu Xi to lead troops into Jiangdong and actively manage the new land. Xu Xi first established Changxing and Guihua towns, as well as Zhouguo and Guizhou. In 995, Anyi and Xinghua towns were built. In 996, Xuanzhou and Mengzhou were established, and activities were set up in the lower reaches of Yalu River. "Take Li Chenggan as the ambassador to change the crossing into Chen Gong" to manage the crossing affairs. At this point, North Korea completely expelled Nuzhen from the left bank of Yalu River and became the territory of North Korea.