At that time, Loulan Kingdom was still a weak country near Lop Nur. After the opening of the Silk Road, Loulan became the hub of Chinese and Western transportation. Because Loulan Wang Angui colluded with Xiongnu and constantly robbed and killed Chinese envoys on the Silk Road, Huo Guang, a general of the Han Dynasty, sent Fu Jiezi to the Western Regions to assassinate An Gui. Fu Jiezi came to Loulan with an assassin, pretending to reward An Gui with gold coins. An Gui was overjoyed and invited Fu Jiezi to drink together. Fu Jiezi was drunk on purpose, helped him to the screen and ordered two assassins to kill An Gui. The left and right princes and nobles fled when they saw it. Fu Jiezi immediately summoned Loulan nationals: "King An Gui committed a capital crime against the Han Dynasty, and the son of heaven sent me to kill him. Now the army of the Han Dynasty has arrived, replacing Wei Tuyan, the younger brother who was taken hostage in Chang 'an, with a new king. "Fu Jiezi beheaded An Gui, sent the trotters back to Chang 'an and hung them under the north gate of Chang 'an Weiyang Palace.
After the rebellion of Loulan was put down, Emperor Zhao of Han Dynasty appointed Wei Tuyan as the new king, changed Loulan to Shanshan, awarded the national seal, and gave ladies-in-waiting wives and a large number of chariots and horses. When leaving, Wei Tuyan said to Emperor Gaozu Zhao Di, "I have lived in Chang 'an for a long time, and now I want to go back to be king. I'm afraid I can't convince the public by myself. Besides, the former prince is still here, afraid that he will kill him when he comes back. Loulan State-owned Yixun City is a rich and beautiful oasis. The son of heaven can send generals to cultivate fields and accumulate valleys there, and let ministers rely on them. "
So the Han Dynasty sent a Sima to lead 40 troops back to the Western Regions with Wei Tuyan. After Wei Tuyan succeeded to the throne, in 77 BC, he moved the capital from the ancient capital of Loulan (Fangcheng) on the north bank of Lop Nur to Mud City (now Ruoqiang County), and the Han Dynasty also established Yixun City (Milan Ruins 36 Regiment) to the east of Mud City. Since then, Loulan's old capital has never developed again. It is estimated that only the former royal nobles still live here. The excavation of Loulan's noble tomb in 2003 also illustrates this point. There are six theories about the disappearance of Loulan. One is that Loulan disappeared in the war. After the fifth century, the kingdom of Loulan began to weaken, the northern powers invaded, and Loulan City was broken and then abandoned.
Statement 2: Loulan was defeated by drought and water shortage, and the ecology deteriorated. After the upstream river was cut off, people had to leave Loulan. Loulan promulgated the world's earliest environmental protection law discovered so far.
Statement 3: The disappearance of Loulan is related to the north-south migration of Lop Nur. Sven Hedin thinks that the period of north-south migration of Lop Nur is about 1500 years. More than 3,000 years ago, there lived a European ethnic tribe in Loulan area. Loulan once again entered a prosperous era more than 1500 years ago, which was directly related to the wandering of Lop Nur.
Statement 4: The disappearance of Loulan is related to the opening of the North Road of the Silk Road. After the opening of the Silk Road North Road through Hami (Yiwu) and Turpan, the Silk Road Desert Road through Loulan was abandoned, and Loulan lost its former glory.
Statement 5: Loulan was destroyed by the plague. A plague from other places claimed the lives of nine of the ten residents in Loulan City. Those who survived by luck fled Loulan and fled other places.
Statement 6: Loulan was defeated by biological invasion. An insect introduced from the two river basins has no natural enemies in Loulan, lives in the soil, can live in the albic soil in Loulan area, and enters the houses in droves. People can't destroy them and have to give up the city.