[quote=@Maavoimat]
The Han Dynasty defeated the Romans in an expedition into central Asia, primarily because the bolts penetrated Roman armor and shields. 
[/quote]

Are you referring to the Battle of Zhizhi? Because if you are, that is kind of a bad example. Firstly, only about a hundred Roman soldiers were supposedly involved, and this is only speculated because the men were said to have fought in a formation that resembled the Roman testudo. It has never actually been proven that it was Romans. And if even if it had been, it was hardly an "expedition", and not a true battle between Romans and Han Chinese.