...[In the Warring States Period], the art of war in China was radically transformed in weaponry, strategy, and army size. Iron now provided stronger, more durable weapons. Early in the Warring States Period, the Chinese adopted the crossbow, raising it to a weapon of great sophistication. It was also during this epoch that cavalry replaced chariots as the primary mobile arm. Threats from nomadic horse people just to the west and north of the Chinese states encouraged the turn to cavalry. In fact, the king of the Choa reformed his cavalry dramatically in 307 [B.C.E.], ordering his soldiers to wear barbarian-style trousers and tight-fitting sleeves in place of robes and to ride horses and learn mounted archery. These cavalrymen lacked stirrups until the end of the Han [Dynasty], and saddles were rudimentary; understandably, this hampered the effectiveness of men on horseback. Therefore, cavalry at first supplemented chariots rather than replacing them, but chariots eventually gave way....
— John A. Lynn, Battle, p. 36
