To the Arabs, the Persians invented the stirrup.
Reality: The stirrup was invented in Korea in the 5th Century. It may have come to the Arabs from the Persians.
There was a crisis in Islam caused by its internal conflicts. A corrupt Caliph was murdered. If you were then opposed to his murder you supported corruption. If you did not support the Caliph, then you were in league with a murderer.
That conflict echoes down to the dispute between the Shi'ite and the Sunni even today.
The conflict: A Caliph who claims the backing of a perfect, powerful, and just G-d must himself be perfect, powerful, and just. If he ever is found to be less than perfect, then that is evidence that Allah is either less than perfect, less than all powerful, or else has withdrawn his favor.
There is no answer. If Osama proved the power of Allah on 9/11, then his loss of his base in Afghanistan has proved the withdrawal of Allah's favor.
What are you some kind of a KOOK? (Keeper of odd knowledge )
Via the Mongols. It was the Mongols who first used the stirrup to great effect, allowing them to fight from horseback, remaining both lethal and mobile at the same time.
My take is that both the Persians and the Arabs learned about the stirrup from Genghis and his boys. Experience is the cruelest teacher, but it's also the most effective.