The Rashīdī History 7.1.7

7.1.7

But if these were approximately and usually the limits, it does not follow that they were, on the one hand, never overstepped, or on the other, that the area they included was always held intact. As a matter of fact, they varied considerably from time to time. Before the rise of Timur, for instance, invasions, by the Moghuls, of Shash, Turkistan and even Mavara-un-Nahr were of common occurrence, while at times in their later history, they extended their sway over districts in the east which did not properly belong to Alti-Shahr. In the same way, when the affairs of their neighbours were in the hands of strong rulers, portions of Moghulistan were cut off for a time, and numbers of the inhabitants seem to have had no scruple in joining the service of the successful conqueror of the time being.