Assertion: gunpowder's use | /r/HasProperty | revealed at the battle of yarmouk
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text: The best use of this lightly armed fast moving cavalry was revealed at the Battle of Yarmouk (636 AD) in which Khalid ibn Walid, knowing the skills of his horsemen, used them to turn the tables at every critical instance of the battle with their ability to engage, disengage, then turn back and attack again from the flank or rear.