Chengis Khan pretty much invented modern warfare, and he and his luitenants invented getting around. Subudai needed only for Khan Oktai to live another two years and he'd have been the first military commander in the history of the planet to have stood on both the Atlantic and Pacific shores of Eurasia. Those guys were moving entires armies 100 - 200 miles per DAY and were getting messages from Beijing to Moscow in a week.
The problem the Mongols did solve - though only briefly - was internal political faction on the steppe, allowing uniform recruitment and projection beyond it in all directions, to loot. (Every time a unified army left the steppe, it conquered something - nothing new in that). Once they had places looted, however, they had no remaining principle of unity, and broke up into separate hordes. When they conquered places, they brought a few traditions of steppe court life and changed dynasty bloodlines, and otherwise were assimiliated by the vastly more populace places they grabbed. When Tamurlane tried to put a unified empire back together, all he could do was loot various pieces of it in succession, depopulating them in the process, and leaving nothing.