The Mongols are a civilization that are known for being the exception to many historical phenomena. Listed below are some of the most important of those exceptions in a generalised form:
- Nomads: The downside is that you have to move around a lot because your herd always needs new grass, which makes it hard to build cities, unless you are the Mongols.
- Civilization: Certain conglomerations of humans are seen as civilizations, where as, say nomadic cultures generally aren’t. Unless you are, say it with me, the Mongols.
- Early Cities: The city-state period in Mesopotamia ended around 2000 BCE, probably because drought and a shift in the course of rivers led to pastoral nomads coming in and conquering the environmentally weakened cities, and then the nomads settled into cities of their own as nomads almost always will, unless, wait for it, you are the Mongols.
- Persian Empire: Let’s start with the Persian empire, which became the model for pretty much all land-based empires throughout the world. Except for, wait for it, the Mongols.
- Silk Road: […] with the growth of the Silk Road, the nomadic people of Central Asia suddenly become much more important to world history. Much of Central Asia isn’t great for agriculture, but it’s difficult to conquer, unless you are, wait for it, the Mongols.
“A tiger wearing a bell will starve.” – Mongolian proverb
- Early Christianity: Both Herods ultimately took their orders from the Romans, and they both show up on the list of rulers who are oppressive to the Jews, partly because there’s never that much religious freedom in an empire, unless you are, wait for it, the Mongols… or the Persians.
- Early Islam: It’s common to hear that in these early years Islam quote “spread by the sword”, and that’s partly true, unless you are — wait for it — the Mongols.
- Dark Ages: [The Abbasids] hailed from the Eastern, and therefore more Persian, provinces of the Islamic Empire. The Abbasids took over in 750 and no one could fully defeat them; until 1258, when they were conquered by, wait for it, the Mongols.
- Islam in Africa: Until then, most of the people living in the East had been hunter-gatherers or herders, but once introduced, agriculture took hold, as it almost always does. Unless, wait for it, you’re the Mongols.
- Imperialism: So by the end of the 19th century, most of Africa and much of Asia had been colonized by European powers. […] Notable exceptions include Japan, which was happily pursuing its own imperialism, Thailand, Iran, and of course Afghanistan. Because no one can conquer Afghanistan, unless you are, wait for it, the Mongols.
- World War II: So, not to sound jingoistic, but the entry of the U.S. into the war really did change everything, although I doubt the Nazis could’ve taken Russia regardless. No one conquers Russia in the wintertime, unless you are, wait for it, the Mongols.
“A donkey that carries me is worth more than a horse that kicks me.” – Mongolian proverb
 Green. J. (2012) Crash Course World History
 Actually, as usual, the truth is more complicated. Many people, including the Mongols, but also including lots of people in Central and East Asia, embraced Islam without any military campaigns.
I suppose that coming from the harsh Steppes of Eastern Asia can harden one to almost anything.
There is a truth in that definitely.
John Green led me here