How did Silla and the Tang Dynasty reach a border agreement?

Li Chenggui was born in Silla. His father, Li Zichun, is a local tycoon and once served as the governor of Shuangcheng. 1356, North Korea attacked its territory, and Li Zichun surrendered and became the military envoy of Northeast China. 1362, Li Chenggui attacked his father's post and took part in the military action to resist the invasion of Jurchen nationality and Mongolian remnants in Tumen River and Yalu River. Soon transferred to Beijing, and then went to the south to resist the Japanese. 137 1 year, in charge of government affairs. 1392, the former king was abolished and succeeded to the throne, and the country name was changed to Korea.

North Korea is located in the eastern part of the Asian continent, bordering the Sea of Japan in the east, the Yellow Sea in the west, Japan across the sea in the south and the Russian Far East in the northeast.

The Korean peninsula is mountainous, and the terrain gradually decreases from northeast to southwest. Most rivers flow to the west and south. The peninsula is rich in minerals, forests and water resources.

North Korean residents migrated from the northern mainland. BC 1 1 In the middle of the century, after China and Zhou Wuwang conquered Zhou, Shang nobles refused to leave Zhou and led a group of merchants to immigrate to Korea. Zhou Wuwang later named Kiko as the North Korean Hou. Kiko then returned to China to accept the title. After returning to North Korea, he established political power in his own name, with Wang (now Pyongyang) as his capital. So some people call it "Ji's Korea".

In BC 195, a Yan man named Wei Man fled to North Korea. Relying on tens of thousands of mainland immigrants who took refuge here, they overthrew Ji's surname Korea and became the king of Korea, which was called "Wei's Korea" in history.

In BC 109, Emperor Wu of the Han Dynasty sent an envoy to woo Wei Guogaoli, who not only refused to obey the imperial edict, but sent troops to attack Liaodong. So Emperor Wudi sent troops to destroy Weishi Korea in one fell swoop. The following year, Le Lang, Lintun, Fan Zhen and Xuantu were established in this area by the Han Dynasty, which were collectively called "Han Four Counties". The North Koreans refused to accept it, and the resistance struggle continued. Twenty years later, the Han government had to cancel these settings. The Korean peninsula is divided and ownerless.

In 37 AD, Prince Zhu Meng of Koguryo in the northern part of the Korean Peninsula unified the surrounding tribes and established the Koguryo State. Around A.D., the Mahan tribe in the south of the peninsula established the Baekje State. In the 3rd century, Silla was established in Gyeongju area of the peninsula. As a result, the situation of tripartite confrontation between the three countries was formed, which is known as the "Three Kingdoms Era" in history.

In order to expand and annex, the three countries kept fighting. In the 4th-5th century, Koguryo was the strongest, and Baekje and Silla were constantly attacked. Baekje was afraid of a blow, and the capital moved south again and again, and its territory was shrinking day by day. By the 6th century A.D., Koguryo was declining due to civil strife and being hit by the Sui Dynasty in China, and Silla gradually became a powerful country among the three countries.

In the 7th century, Silla formed an alliance with China in the Tang Dynasty. Baekje was destroyed in 660 and Koguryo was destroyed in 668. In the Tang Dynasty, the Governor's Office of Anton was established in Pyongyang, which directly governed Goguryeo and Baekje, and a puppet regime was established in Baekje.

Silla was dissatisfied with the dominance of the Tang dynasty, supported the resistance of the Koreans under the jurisdiction of the Tang dynasty, and directly sent troops to harass, forcing the Tang dynasty to retreat step by step. In 767 AD, the capital of the Tang Dynasty moved to Liaodong, and Silla occupied the territories of Baekje and Koguryo. In 735 AD, the Tang Dynasty reached a border agreement with Silla, with the Datong River as the boundary and the southern region under the jurisdiction of North Korea. Silla unified the whole peninsula.

Later, due to civil strife, the central government of Silla was unable to control the whole peninsula, and its rule was limited to the southeast corner of the peninsula. In the areas that originally belonged to Baekje and Koguryo, two regimes, Post-Baekje and Post-Koguryo, emerged. In this way, Silla, post-Baekje and post-Koguryo formed a three-legged situation on the Korean Peninsula, which was called the post-Three Kingdoms in history.