Sclavs

 s quote several excerpts:

Procopius, Book VII, XIII - describing the events in year 545 AD:

"(...) For a great throng of the barbarians, the Sclaveni, had, as it happened, recently crossed the Ister, plundering the adjoining country and enslaved a very great number of Romans. (...)"

Another excerpt from Procopius:

"(...) In Illyria and Thracia, from the Ionian Gulf to Byzantine surrounding cities, where Hellas and Chersonese regions are situated, (...) the Sclavenes and the Antes, penetrating practically every year since Justinian administering the Roman Empire, were inflicting irreversible damage to their inhabitants. In each invasion I estimate 200,000 Romans were either enslaved or killed (...)"

And here an excerpt from John of Ephesus:

"(...) In third year after the death of Emperor Justin, during the reign of victorious Tiberius, the damned nation of the Slavs has risen, and marching through entire Hellas, through lands of Thessaly and Thrace, captured many cities and strongholds, plundered, burned and robbed, seized the land and settled there with full ease, without fear, like in their own land. (...) they were plundering the country, burning it and robbing, as far as the Great Walls [of Constantinople], and this is how they captured many thousands of cattle, as well as many other kinds of booty. (...) Until today, that is until year 584, they still continue to live in peace in lands of the Rhomaioi, without fear and concern, plundering, enslaving and burning, getting rich and highjacking gold and silver, capturing horses and plenty of weapons; and they have learned to fight better than the Rhomaioi. (...)"

Also a passage from Menander Protector:

"(...) About the fourth year of the reign of Caesar Tiberius Constantine, some hundred thousand Slavs broke into Thrace, and pillaged that and many other regions. As Greece was being laid waste and enslaved by the Slavs, with trouble liable to flare up anywhere, and as Tiberius had at his disposal by no means sufficient forces, he sent a delegation to the Khagan of the Avars. (...)"

Jordanes about the three branches of early Slavic peoples (ethnonym Slavs comes from just one of them):

"(...) These people, as we started to say at the beginning of our account or catalogue of nations, though off-shoots from one stock, have now three names, that is, Venedi, Antes and Sclaveni. (...) they now rage in war far and wide, in punishment for our sins (...) Though their names are now dispersed amid various clans and places, yet they are chiefly called Sclaveni and Antes. (...)"

Procopius of Caesarea once again (about Slavic foederati/mercenaries fighting under Belisarius):

"(...) Belisarius was eager to capture alive one of the men of note among the enemy, in order that he might learn what the reason might be why the barbarians were holding out in their desperate situation. And Valerian promised readily to perform such a service for him. For there were some men in his command, he said, from the nation of the Sclaveni, who are accustomed to conceal themselves behind a small rock or any bush which may happen to be near and pounce upon an enemy. In fact, they are constantly practising this in their slave hunts along the river Ister, both on the Romans and on the barbarians as well. (...)"

And also: http://www.ascsa.edu.gr/pdf/uploads/hesperia/147272.pdf

"(...) There is clear evidence from the excavations of the Athenian Agora that the late sixth century witnessed some interruption in the peaceful course of town life in Athens. Certain buildings, for example, are known to have been burnt and temporarily or permanently deserted at that time. Finds of coinage, evidently concealed in haste or abandoned in emergency and never recovered, allow a date to be assigned to events, for which, although they are well attested by archaeological discovery, it would otherwise be very difficult to demonstrate a particular historical context. Byzantine chroniclers tell of a Slavonic invasion of Greece which took place apparently at the end of the year 578 or early in 579, as a result of which large numbers of Slavs settled in Greece... It is virtually certain that some of the destruction in the Athenian Agora, for which a date in the years immediately following the invasion is here proposed, was the work of the Slavs... Menander Protector, in his work chronicling the period ca. 560-580, writes as followers..."