The Great Wall of China was, it turns out not necessarily built for defense against invaders.  At least not the northern segment which is mostly in Mongolia. For the first time, researchers from an Israeli-led international team has fully mapped out over 700 kilometers of The Northern Line which was built about 800 year ago just before Genghis Kahn reigned. Prof. Gideon Shelach-Lavi, professor in the department of Asian studies at the Hebrew University of Jerusalem, told reporter Arieh O’Sullivan that the wall was mainly used to monitor and control the movement of peoples.