So fun story, the worst enemy the Mongols faced during the era of expansion under Genghis/Temujin was probably alcohol. Mongols traditionally drank a fermented milk beverage which had very low alcohol content, weaker than the weakest beers, thus the drinking culture encouraged very heavy consumption, even to the point of inducing vomiting to make room for more. However when they began conquering settled peoples they gained access to distilled grain and fruit alcohols which were much stronger and became popular. However the drinking culture couldn't really change overnight to compensate so it was only considered appropriately manly to down wine or spirits liters at a time. This was devastating to the upper ranks of society that could afford to indulge in stronger alcohol frequently, with many nobles dying in their 30s or 40s.