All fair points. My understanding of their cavalry tactics is that they followed a very rote playbook. They would send out light cavalry to engage the enemy forces, inflict light damage, and then ride away at just sufficient speed to get the enemy to chase them. They would then have much heavier cavalry and infantry waiting, usually behind some sort of visual screen, to stop the enemy advance cold. And then they would advance and slaughter all before them. They didn't concern themselves with siege tactics or supply lines or logistical complexities until they really established their empire, and only incorporated more advanced tactics and strategies once they had conquered more sophisticated but slower enemies.

The history of the Mongols shows that they were not, in fact, invincible. They were defeated quite badly by the Persian Khwarezmi at one point. So they could be beaten, and were, several times – but they only really stopped advancing when their Khans kicked the bucket.

Their genius, however, was in their morale. Sure, they couldn't take a European soldier in anything even close to a fair fight… But they would raid the town first, slaughter everyone but the women and children, and then drive the dependents into the teeth of their own fathers and husbands.

they would create mountains of skulls and betray anyone that surrendered, and they dodn't 'conquer' cities, they utterly razed them, then threw their young men into their 'horde' and used the survivors as slave labor. Terror was their only effective weapon, and by the time they started hitting the more heavily defended northern European cities, they had swelled their armies to a thousand times their original size… after all, the 'whites' making out their infantry were valueless, and they could afford to spend them a HUNDRED to one on their next victory.

There is a very interesting story that used to be told around Germany, about a heavily-armed merchant convoy that was confronted by a mongol.

The Mongol demanded that they surrender, and the Merchant immediately complied and gestured for his Guardsmen to stand down. The Mongol then ordered them to line up and kneel before him.

He started beheading the guards, one by one. An injured Knight who had been riding in the wagon stepped out, saw what was happening, and noticed that three guards had already been killed. He yelled "What the hell is going on?".

The Guardsman that was closest to him turned his head and hissed, "Shut up, Man, do you want to piss him off?"

The Knight, of course, strode over and beat the Mongol to death with his crutch.

They were not… skilled warriors, comparatively. Their deeds were spoken of with awe by Generals and Leaders who would never admit losing to an inferior foe, and built their mystique and terror until trained warriors would foul themselves and the first sighting. It was an empire built on Propaganda, which is why it fell apart 5 years after Ghengis' death.

But boy, did it work for them.