Persian Huns Arab Mongolian

Well, how old are you thinking "ancient"? The Persians were in the time I would most closely think of "ancient" and that would deal with Classical Greece... a pretty bad lot actually. I consider the Muslim conquests pretty modern in contrast - after all, the same folks that rid Spain of the last of them also set Columbus across the Atlantic... Actually the Huns and the Mongols were probably the same folks, at some point or another anyway. The Huns contributed to the fall of the Western Roman Empire and the separate, later, Mongol invasion disrupted medieval life. I suspect that the effects of the Muslim conquests are more felt because they ruled and converted large parts of the areas they had.