In 221BC, the state of Qin completed its conquest over the other Warring States and united China under Qin Shi Huang, the first emperor of China. These conquests, combined with the Legalist reforms started by Shang Yang in the 4th century BC, transformed China from a loose confederation of feudal states to an authoritarian empire. With the transformation, Qin became able to command a far greater assembly of labourers to be used in public works than the prior feudal kingdoms. Also, once unification was achieved, Qin found itself in possession of a large professional army with no more internal enemies to fight and thus had to find a new use for them. Soon after the conquests, in the year 215 BC, the emperor sent the famed general Meng Tian to the Ordos region to drive out the Xiongnu nomads settled there, who had risen from beyond the fallen marginal states along the northern frontier. Qin's campaign against the Xiongnu was preemptive in nature, since there was no pressing nomadic menace to be faced at the time; its aim was to annexe the ambiguous territories of the Ordos and to clearly define the Qin's northern borders. Once the Xiongnu were chased away, Meng Tian introduced 30,000 settler families to colonize the newly conquered territories.