Warring States Period (475–221 BC) was an era of division in ancient China. After the relatively peaceful and philosophical Spring and Autumn Period, various states were at war before the Qin state conquered them all, and China was reunited under the Qin Dynasty. The State of Chu, one of seven superpowers during the Warring State period. Chu state have the largest territory and the best technical know how in terms of weapon production. At 475-221 BC, while most of the world is still in the Bronze age, Chu was the first culture that transitioned into the Iron age, iron was widely used in tools and weaponry. The Chu Jian were much longer, lighter than their bronze counterparts and was feared among their rivals. Long Chu Jian was the first long double hand military Jian in Chinese history.