Qin army was first to organise an army with most effective professional army that included Horse melee units and Horse archer units, they learnt the tactics from fighting against the Xion Nu. and there have being movement to abandoned main form of horse chariots tactics in favor of more mobile Horse back units. but chariots are still in use. the bulk of the Zhang Gou or warrning state army is sitll foot soldiers. but Qin had the best logistical system out of all the warring kindoms. and thats how it won the day at the end. united the First empire of china.