After the barbarians sacked Rome, the dark ages that followed lasted 1000 years in Europe. If the Islamists do realize their dream of world conquest, I wonder how many centuries it will take mankind to throw off the yoke of ignorance and build a new civilization.
Really, the whole “Dark Ages” construct is quite inaccurate. For starters, check out this video:
https://www.youtube.com/watch?v=Cqzq01i2O3U