For the East Roman Empire, the seventh century was a time of almost continuous troubles. The mutiny in 602 and the murder of the Emperor Maurice plunged the Empire into anarchy. In 604 the Persians started to invade the Empire’s Asian provinces, while the Slav Völkerwanderung from the north bank of the lower course of the Danube swamped the whole of the interior of the Balkan Peninsula. The Empire had hardly begun to recover from the last and worst Romano-Persian war of 604-28, when the Arabs launched their assault in 633. The climax of this assault was the Arab siege of Constantinople in 674-8, and this peril had only just been surmounted when, in 680-1, the Eurasian nomad Bulgars established a permanent foothold on the south bank of the Danube.
At the first Arab siege, napalm or Greek fire was first used. There was a second Arab siege in 717-18. The Bulgars were not Slavs, but by the tenth century had become slavicised.
The founder of the First Bulgarian Empire in 681 was Asparukh.
Mankind and Mother Earth, OUP, 1976, posthumous