Quote Originally Posted by k_raso
That much is true, since the romans had a much harder time conquering the barbarian tribes in Iberia, Gaul and Britannia (and Germania for the brief period that was under roman control) than fighting the successor states in the east and in Egypt.

Should they had stood together, there may have never been Islam.
Well actually you're early. Had Rome stayed together they might have defeated Islam. Its a shame Demetrius' decendants could never hold a large Empire together, his was the most stable dynasty.