At the beginning of the establishment of the Han Dynasty, it faced the threat of the great enemy of the Xiongnu in the north. During the Qin Dynasty, although the Xiongnu were a threat to the Central Plains Dynasty, they were still limited to harassing the borders, and it was difficult to make the Central Plains Dynasty submit. By the time Mo Dun ruled over the Xiongnu, the Xiongnu forces had grown and developed, defeating many countries in the Western Regions and becoming the overlords of the Western Regions.
After Liu Bang established the Han Dynasty, he originally wanted to conquer the Xiongnu, but he almost lost his life. Since then, the Han Dynasty has maintained a relatively stable diplomatic state by fighting with the Xiongnu. This kind of low-pitched peace could have ended prematurely, but as a result, because a eunuch sent to the Xiongnu and his relatives defected to the enemy, the Han Dynasty has been passively beaten for nearly a hundred years. This eunuch was called the Bank of China, and judging from his name, he was not a good man. Originally, the Bocq said that he did not want to follow the he and his relatives to the Xiongnu, but he could not disobey the emperor's will and could not avoid this matter, so the BOC said that he chose to surrender, and he was also given preferential treatment by Shan Yu. Before the Bank of China said that before going to the Xiongnu, it had seen the Han Dynasty send and pro-Xiongnu. The he and relatives not only sent the princess over, but also brought some costumes, labor tools, etc., and the etiquette and culture of the Han people were also brought along.
The Bank of China said that it was the Han Dynasty's desire to implement cultural assimilation to eliminate the hidden danger of the Threat of the Xiongnu, so that the Huns could abandon their own culture, so the BoC said that it told the Xiongnu Shan Yu the reason for this. Shan Yu learned that this was a conspiracy of the Han Dynasty, and after that, he resolutely resisted the culture passed down by the Han Dynasty, and the measure of "cultural invasion" thus lost its effect. The Bank of China said that after defecting to the Xiongnu, it also helped Shan Yu to come up with many crooked ideas to deal with the Han Dynasty. He persuaded Shan Yu to take advantage of the period when the other party was quietly seeking peace, and asked for treasure from the other party, which would not make the Han Dynasty bear a great loss.
At that time, the main support for the strength of the Central Plains Dynasty was agricultural harvest, such as war is closely related to logistical support, if there is insufficient food, the combat effectiveness of the army will be significantly weakened. It can be said that agricultural harvest is an important influencing factor in the strength of the Central Plains Dynasty. The Bank of China said that he was naturally very clear about this, and he told Shan Yu that as long as he raided the Han Dynasty agricultural planting areas before the Han Dynasty's agricultural harvest, the Han Dynasty would not be able to obtain a good harvest. By adopting his advice alone, the Han Dynasty became more and more passive, and it was difficult to compete with the Xiongnu. There are many traitors like the Bank of China in history, who, for their own interests, choose to betray the country to help the enemy country. Because they knew what the weaknesses of the Central Plains Dynasty were, after they defected to the enemy countries, they targeted these weak points of the Central Plains Dynasty and helped the enemy countries to oppress the Central Plains Dynasty more effectively.
But even though they gained a lot of benefits, they also left a reputation for infamy. There is no record of the outcome of the BOC's statement, and during that period, such a traitor may have escaped justice. Although the Han Dynasty was oppressed by the Xiongnu for nearly a hundred years because of the Zhonghang Theory, during the period of Emperor Wu of the Han Dynasty, the strength of the Han Dynasty developed enough to match the Xiongnu. Emperor Wu of Han sent Wei Qing and Huo Toyi to lead an army to take the initiative to attack the Xiongnu, and the Xiongnu were repeatedly defeated and retreated.
It can be seen from this that the strength of a country will have differences in strength and weakness at different times, and even if a country has only been bullied for a period of time, it cannot be considered that it has no possibility of developing a strong one. The Xiongnu oppressed the Han Dynasty for so long, and as a result, after being defeated by the Han Dynasty, they never returned to their original level of strength.