匈奴明明已经被秦始皇打败,为何他不乘胜追击,而是修长城防御

匈奴明明已经被秦始皇打败,为何他不乘胜追击,而是修长城防御

匈奴明明已经被秦始皇打败,为何他不乘胜追击,而是修长城防御