Genghis Khan's greatest legacy isn't the empire he built, but the rules he followed

When the Mongols conquered new lands, they would often follow Genghis' famous rules of war, which were:<br><br>1. The elderly and children will not be harmed.<br>2. Women will not be violated.<br>3. Professional people, such as doctors and priests, will not be killed.<br>4. Anyone else will be free to leave with their belongings.<br><br>In other words, these rules meant that civilians wouldn't be targeted, and could leave safely once they'd been given notice to do so. This is quite a contrast to how the Romans fought, who were quite brutal in their conquests, or how the Nazis would fight, who were also brutal in their conquests.<br><br>The rules of war that Genghis set out meant that he didn't have to fight his way through civilian populations, because he didn't target civilians, and that, combined with the fact that he was a brilliant and honourable leader who was a great tactician, allowed him to conquer lands efficiently and cheaply. This is why, for all the destruction that the Mongols caused, the Mongol Empire didn't last nearly as long as, say, the Roman Empire. The Mongols didn't have a tax base or any sort of long term investment in the places that they had conquered, because they didn't really try to assimilate into local populations. When they had extracted resources or manpower from a place, they moved on.<br><br>The Mongols left behind the Silk Road, a network of trade routes that were built as a result of Genghis' rules of war, because different parts of the empire could trade with each other safely, because they were all following the same set of rules.<br><br>The rules of war that Genghis followed also allowed different cultures to live together peacefully, and to intermarry. As a result, the Mongol Empire had a lot of genetic diversity, which was quite unusual for a warlike society. Even in ancient Egypt, where the pharaohs married their sisters, there was less genetic diversity than in the Mongol Empire.<br><br>In short, Genghis' greatest legacy was setting rules for war, that allowed him and his people to successfully conquer lands without causing massive destruction, while also allowing conquered lands to trade and intermarry, and leaving a lasting genetic legacy to this day.