So yes, as an example, Herodotous may have been a Greek political exile ("loser"), but the fact that Arabs managed to destroy substantial chunks of Sassanid Iranian records and archives left the Greek version of the ancient Persia to persist until well into 20th century.
This is the sense of the phrase "history is written by victors". It has nothing to do with the individual historians (since they are not warriors) but with their supporting sociopolitical/cultural context.
> We say that history is written by the winners. That is sometimes true. We have no Carthaginian accounts of their war with Rome; few historians today have much sympathy for Hitler. But the thread that seems to connect many of the great histories of the pre-modern world is that they were written by the losers.
However, when we only have one account it's hard to judge accuracy.
In principle, the text of history is never the same as what really happened. What a historian can do is to do his best to write down what he verifies, the different accounts that have merits but none of them can be verified as the ultimate truth. As a reader of history, we should appreciate both the text and the effort, study it and learn our lessons.
Sima Qian's work covers not only the period of his life, but since the beginning of Chinese civilization. He read extensively, touched on all the texts he could get access to (his position in the government granted him such privilege, even after he was punished.) He often travelled out to verify the texts. Considering that was almost 2000 years ago and the size of China (although much smaller than now), one must respect his efforts.
I would say Sima Qian gave a comprehensive and objective depiction of Han Wudi, the emperor who punished him. Wudi was one of the greatest rulers in Chinese history. Sima Qian gave due credits to Wudi, while he didn't hesitate to write down his dubious policies and his mistakes, both before and after his punishment. Wudi knew his work, and didn't interfere. He punished Sima Qian for Sima's opinions on Li Ling (although Wudi was both wrong and brutal in this case), but not by his depiction on Wudi in his work.
I think it is fair to say Sima Qian is "one of two men who can claim to have invented history". His work is the standard and the gauge of all the historians that followed him. Not many have his talents and his balls.
Sima Qian's work is also a classic in literature. For anyone who studies ancient Chinese literature, he must study is work, the Records of the Grand Historian (Shiji).
Because you really can't trust anything originating from a single source.
