And one of the causes often given for the rapid spread is that you had relative stability formed by these khanates so that trade was able to happen. But with that trade, you also have the spread of disease. And so the bubonic plague, or the Black Death of the 1330s, in particular does damage to the Il Khanate in Persia and the Middle East. Not only the emperor, but his sons all die from the bubonic plague. And so you see here on this timeline, the Il Khanate goes into a rapid decline because of the Black Death. And at the same time, in the southwest corner of the Shagatai Khanate, a future conqueror is born. Timur, which means iron.