And Arabia exported incense and spices and tortoise shells. Oh god, it's a red one, isn't it? It's just gonna chase me. I just... Ow! Up until now on Crash Course, we've been focused on city-dwelling, civilizational types. But with the growth of the Silk Road, the nomadic peoples of Central Asia suddenly become much more important to world history. Most of Central Asia isn't great for agriculture, but it's difficult to conquer unless you are, wait for it, the Mongols.