The Mongols were more successful at emerging from central Asia where larger groups were not due to several factors:
1- The Mongols had the advantage of having Genghis Khan with them
2- Their number was much less than that of other pastoral groups
3- They did not depend on civilization for transportation. Instead, they rode horses in order to border the Siberian forest. They depended on hunting, herding and arching for protection and for getting food.