Question: when did the building of the great wall of china begin
Answer: when fortifications built by various states during the Spring and Autumn ( 771 -- 476 BC ) and Warring States periods ( 475 -- 221 BC ) were connected by the first emperor of China , Qin Shi Huang , to protect his newly founded Qin dynasty ( 221 -- 206 BC ) against incursions by nomads from Inner Asia