The story may be a bit more nuanced that that:
From a review of "Genghis Khan and the Making of the Modern World"
"Arguably, however, Genghis Khan and the Mongols were the dominant force that shaped Eurasia and consequently the modern world. Not for what they destroyed – though they wrought much destruction all over the continent – but for what they built. They came close to uniting Eurasia into a world empire, and in so doing they spread throughout it technologies like paper, gunpowder, paper money, or the compass – and trousers. They revolutionised warfare. More lastingly, in the word's of the author: ' ...they also created the nucleus of a universal culture and world system. (...) With the emphasis on free commerce, open communication, shared knowledge, secular politics, religious coexistence, international law, and diplomatic immunity.' ".
> The story may be a bit more nuanced that that:
Make that a lot more nuanced:
(From the same review cited above):
"The Mongols' was the first modern army. It was built on a rational structure (based, like the Roman legion, on units in the multiple of tens) and promotion was strictly on merit. Thoroughly disciplined and highly mobile – infantry was unknown – it could execute complex tactical manoeuvres in silence upon orders from centralised command. Speed and efficiency in conquest were their trademark, and the source of the fear they struck in the enemy. Horse and bow where the Mongol warriors' strength – and it the end their weakness. Forests hindered the deployment of mounted armies, in the humid heat of India the bows failed, and the horses' strength faded when they could not find pastures in the Syrian desert.
Warfare technology and logistics were other factors in the Mongols' superiority. The gunpowder formula was changed to yield explosive force, rather than slow burn as in fire-lances and rockets. Guns and cannon were developed. Specialised troops of craftsmen were skilled in building complex siege machines from local materials – obviating the need to move them over long distances. They perfected sapping of walls, thus making static defence impossible. A dedicated medical corps looked after the wounded. The army and its horses spread across the plains for forage and sustenance, thus obviating for the need for supply lines – yet a sophisticated communication system based on melodies to ensure accurate memorisation allowed the scattered troops to regroup at short notice and to remain in touch with the distant leadership.
The intelligence system was second to none, and the Mongols knew much more about the lands they were about to invade than the defenders knew about the Mongols – if nothing else because the latter lived off the land and needed to know where water and pastures were to be found. In addition, the Mongols developed highly sophisticated methods of psychological warfare, spreading rumours about their cruelty and destruction. This unsettled the rural populations that then fled before the advancing army, hamstringing the defence efforts."