I want to know the answer to the following question:
Where did the Northern Xiongnu flee to in AD 91?
All the background I'm provided with is that "Dou Gu (d. 88 AD) defeated the Northern Xiongnu at the Battle of Yiwulu in AD 73, evicting them from Turpan and chasing them as far as Lake Barkol before establishing a garrison at Hami.". Is that enough to answer the question?
Answer: no