Zhaojun went to the fortress in 33 BC (the first year of Jingning, Yuan Di). At that time, the relationship between Han and Xiongnu was different from that in the early Han Dynasty. From the founding of Liu Bang in 206 BC to the 170 years when Zhaojun left the fortress, the relationship between China and Hungary was intermittent. Before Emperor Wu of the Han Dynasty ascended the throne (BC 140), the policy of the Han Dynasty towards Xiongnu was pro-marriage, because the national strength was weak at that time, and pro-marriage was in exchange for temporary peace on the border. After Emperor Wu ascended the throne, due to the enrichment of national strength, he changed from a policy of intimacy to a policy of war, and used the defense of war as a means to alleviate the invasion and threat of Xiongnu nobles. After several decisive battles, the Huns were defeated one after another. By the end of Emperor Wu, "Xiongnu was pregnant and fell again? , exhausted, miserable, since Khan often and pro-plan "below. Later, in 7 1 BC, Han and Wusun (now a nomadic tribe in the upper reaches of Ili River) jointly attacked, and the Xiongnu was defeated again, and the subordinate ministries also took the opportunity to attack, so "Xiongnu was weak, the princes of various countries collapsed, and it was unreasonable to attack thieves." From then on, the Huns were no longer able to confront the Han Dynasty, and it was thirty-nine years since Zhaojun left the fortress.