Today, while listening to the amazing Hardcore History podcast about The Mongol Invasions, I learned the answer to that question-
Subutai (1176–1248) was the primary military strategist and general of Genghis Khan and Ögedei Khan. He directed more than twenty campaigns in which he conquered thirty-two nations and won sixty-five pitched battles, during which he conquered or overran more territory than any other commander in history. He gained victory by means of imaginative and sophisticated strategies and routinely coordinated movements of armies that were hundreds of kilometers away from each other. He is also remembered for devising the campaign that destroyed the armies of Hungary and Poland within two days of each other, by forces over five hundred kilometers apart. (From Subutai – Wikipedia, the free encyclopedia.)
As you will learn, if you give the amazing Hardcore History episode a listen (I recommend listening to the show in general, and this particular mini-series is one of their very best.) at one point he took a Scouting Force of 20,000 men on a little three year tour of Europe, and in the process conquered 11 nations, including Russia! He did this with fairly small casualties (he still had roughly 3/4 of his men at the end of the “tour”) and this was after fighting numerous battles where his army was outnumbered 2:1 or 3:1! The enemy was usually completely slaughtered with nearly 100% casualties.
There is also no record of him losing a single battle- ever.
Ah, if only Zhuge Liang was still alive when Subutai was, that would have been a glorious fight!