Despite his very large debts to Confucian tradition, Sima was an innovator in four ways. To begin with, Sima's work was concerned with the history of the known world. Previous Chinese historians had focused on only one dynasty and/or region. Sima's history of 130 chapters began with the legendary Yellow Emperor and extended to his own time, and covered not only China, but also neighboring nations like Korea and Vietnam. In this regard, Sima was significant as the first Chinese historian to treat the peoples living to the north of the Great Wall like the Xiongnu as human beings who were implicitly the equals of the Middle Kingdom, instead of the traditional approach which had portrayed the Xiongnu as savages who had the appearance of humans, but the minds of animals. In his comments about the Xiongnu, Sima refrained from evoking claims about the innate moral superiority of the Han over the "northern barbarians" that were the standard rhetorical tropes of Chinese historians in this period. Likewise, Sima in his chapter about the Xiongnu condemns those advisors who pursue the "expediency of the moment", that is advise the Emperor to carry policies such as conquests of other nations that bring a brief moment of glory, but burden the state with the enormous financial and often human costs of holding on to the conquered land. Sima was engaging in an indirect criticism of the advisors of the Emperor Wu who were urging him to pursue a policy of aggression towards the Xiongnu and conquer all their land, a policy that Sima was apparently opposed to.