How did Qin shi Huangdi create the first unified Chinese empire

Qin Shi Huangdi was the king of Qin, one of the several Chinese kingdoms. He achieved the first unification of all Chinese lands in 221 BC. As in other examples of empire creation, Qin managed to build an empire through a combination of economic and technological advantages and military might and prowess. More effective methods of irrigation and farming developed in Qin allowed for larger harvests and increased amount of food; on the other side, the Qin military developed better and more lethal weapons such as a powerful crossbow and a powerful cavalry. This combination of enhanced capacity to feed and sustain a huge army (logistics) and military superiority made it possible to the ruler of Qin to vanquish all the other states, unify China and put an end to the chaotic Warring States Period, a convulsed era of Chinese ancient history.