《汉书·传·李广苏建传》
走了大约几百里，匈奴左贤王带领四万骑兵包围李广，李广的士兵都很恐惧，李广就派他的儿子李敢快马冲击敌人。
行数百里，匈奴左贤王将四万骑围广，广军士皆恐，广乃使其子敢往驰之。
After traveling about a few hundred miles, the Left Xian King of the Xiongnu led 40,000 cavalry to surround Li Guang. Li Guang's soldiers were all terrified. Li Guang then sent his son, Li Gan, to quickly attack the enemy.