The Great Wall of Han has been built for more than 2,000 years, and it has been built for 20 years. This is the project completed in the Han Wu emperor period. On the one hand, General Huo Qi went to the disease to fight the Hunnu and vowed to sweep the Hunnu regardless of his body. On the one hand, Hexi four counties, Dunhuang, Zhangye, Wuwei, Jiuquan, Defend the Huns in two ways.