It was said that if the Northern Huns had been willing to surrender to the Han Dynasty, there wouldn't have been so many issues. After all, when the Huns submitted, the Han Dynasty didn't really mistreat them.
However, in some instances, dignity is paramount. The Northern Huns have stubbornly resisted for three hundred years, making surrender utterly impossible. The Han Dynasty also understands that if the Northern Huns wanted to surrender, they would have done so long ago; they wouldn't have held on for so many years.
Thus, after Zhang Fei and others surrounded over three thousand Northern Hun warriors, there were no more words exchanged. Those surrounded Northern Hun warriors didn't plead for mercy either. There was only one outcome when they met: either you die, or I perish!
This is why on this continent, the Han Emperor regarded other foreign invasions as mere trifles, yet when the Orthodox Xiongnu appeared, no matter how inept they were, they would explode immediately.
