During the East Roman Empire, They sent an army to invade China. After several "Contacts" they failed to conquer China and numbers of their soldiers reduced drastically. They wanted to return to their motherland, the East Roman Empire, but was blocked off by Moslims. Finally that army had to settle down for survival, and they did settle down in a land on the far west of China where is the present Xinjiang province.
What I want to remind you is that China had fought with the west, the East Roman Empire and won.

P.S. The native Xinjiang people are decendents of the East Roman Empire.