汉朝时,汉武帝派苏武为使臣去匈奴示好,不想匈奴单于却把苏武扣押起来,逼其投降。苏武宁死不降,单于就把他送到寒冷的北海放羊。单于招降苏武之心不死,把他的心腹卫律和虞常变成白羊和黑羊,跟随苏武而去,以便监视苏武,看他意志是否动摇,肯不肯归降匈奴。其实单于的诡计已被苏武识破。苏武每天放羊前,就把卫律变成的白羊拴在帐篷 During the Han dynasty, the Han Wudi sent Su Wu to minister to the Huns and did not want the Hun to detain Su Wu and force him to surrender. Su Wuning die does not drop, just sent him to the cold North Sea Sheep. To surrender to the heart of Su Wu alone, his heart and soul and law often become white sheep and black sheep, followed by Su Wu away in order to monitor Su Wu, see if he will be shaken, willing to return to the Huns. In fact, the only trick in the Su Wu have been identified. Su Wu before the sheep, put the law into Aries tied to the tent