Even when routed or pursued by a determined enemy, the Mongols employed still more tricks with which to save themselves.
If they were surprised and overtaken while on patrol, they usually carried some valuable items with them to strew on the ground as they escaped.
The enemy invariably broke ranks to retrieve the goods, often fighting among themselves to do so, and thereby allowed the Mongols to escape.
At other times, the Mongols threw sand in the wind or tied tree branches to their horses’ tails to whip up the dust in order to obscure their movements or to make the pursuers think that the Mongols were in much greater numbers than they actually were.
from Jack Weatherford's 'Genghis Khan and the Making of the Modern World'
https://www.amazon.com/dp/B000FCK206