 FACT: When Shan Yu (Mongol leader) talks to the Chinese soldiers, he  mocks that the Emperor "invited" him, "by building his Great Wall to  challenge my strength." Even though we do not know what time period  this is exactly, the wall took well over a few hundred years to  build and therefore the emperor that planned to do so would not have  survived upon its completion. Despite the fact that it was rebuilt  significantly in the 16th and 17th centuries, it was after the Huns  had ceased to be a threat.