Descendants of a detachment of troops dispatched from the Manchurian capital Mukden to Xinjiang in 1764

From Empires of the Word by Nicholas Ostler.  Page 143.

Then the Tungus-speaking Jurchen people, now to be known as the Manchus, gained a second chance to dominate China. This invasion was the last permanent penetration of China by speakers of a foreign language.

In the early seventeenth century, the Manchus had been reorganised, under two able leaders, and advanced into the northern marches of Chinese territory to establish a capital at Mukden. Then, in 1644, they had the luck to be invited into Beijing as a tactical move in a struggle between two generals contending to replace the Ming. The Manchus took the opportunity to install themselves, styling their new dynasty with the name Qīng (, ‘Pure’), and by 1651 had put down all resistance in the rest of China. Although they came speaking their own language, and it remained an official written language of the Chinese state until the end of the dynasty in 1911, it had died out in speech even at court by the eighteenth century. The language did not survive even in Manchuria itself, a curious victim of its people’s successful takeover of China and its way of life. Today it is only spoken, under the name of Xibo, by the descendants of a detachment of troops dispatched from the Manchurian capital Mukden to Xinjiang in 1764—a north-eastern language now spoken only in the Chinese north-west.