中国历史 | 长城到底有什么作用？大叔用英语介绍中国长城！

长城并不是很高，那么它到底是如何阻挡游牧民族抢劫农耕民族的？本期视频会详细介绍为什么要修建长城，长城是如何修建的，以及最重要的，长城是如何作为一个系统抵御外敌的。 The great wall of China is not too high to climb over, then how did it prevent the nomadic civilization from looting the farming civilization? This video is going to explain why was the great wall of China built, how was it built, and most importantly, how exactly it works as a system of defense.