They were a bunch of nomadic tribes that defeated some of the most powerful empires of the time. What is it about them that made them so successful, were they motivated, did they have technology that their enemies not have, or were they just lucky?
I have no knowledge on this subject. But to aid in the answering of the question, perhaps you could elaborate on:
What would you quantify as "successful" in this respect? Are you looking at it in terms of:
a) duration of their reign in power (duration of the Pax Mongolica,
or b) extent of their hegemony (how far the Mongolian Empire reached)
These might help to make the answering process easier! Cheers!
I am by no means a historian but I can tell you about some things.
They had a great leader, temujin, known as the great kahn or genghis khan who had as goal to unite the tribes. But when he came across chinese diplomats that helped him fend off the tartars he learned that those same chinese diplomats also helped the tartars, leading to the tartars and the mongols killing eachother, which meant that neither the mongols or the tartars would become a threat to the chinese. This knowledge set temujins vision on conquering the chinese cities after he united the mongols. Thus giving him and his successors the ambition to conquer.
It is said that the armies of the mongols travelled in groups of 10, living of a mixture of blood and milk, both being supplied by their horses. This made them higly mobile, some would say even faster than modern panzer divisions, making it quite a bit easier to control and fight at places so far apart.
As said, I am by no means a historian and I hope someone else could elaborate about what happened after the death of temujin and how they caputered and governed large walled cities.