When did they start building the Great Wall of China ?
The history of the Great Wall of China traditionally began when fortifications built by various states during the Spring and Autumn ( 771–476 ) and Warring States periods ( 475–221 ) were connected by the first emperor of China , Qin Shi Huang , to protect his newly founded Qin Dynasty ( 221–206 ) against incursions by nomads from Inner Asia .