Like I said, in the pursuit of absolute brevity, I often trim the verbiage to the bare minimum, assuming a certain knowledge. Perhaps I can make longer explanation versions for those who need remediation.
Or, even if you had no bloody idea at all where Islam started, you might glance at the map, and the arrows. And the date by Mecca, and the date in Spain. Sheesh.
so much for reasonable criticism. have a nice day