[8] The second book of the Miracles of Saint Demetrius names Perboundos, the "king of the Rhynchinoi",[a] as a powerful ruler, who was sufficiently assimilated to be able to speak Greek, had relations with Thessalonica to the point of maintaining a residence there, and even dressed in the Byzantine style.

At their request, a joint delegation including Thessalonian envoys went to Constantinople to intercede on his behalf—a unique event, according to Byzantinist Paul Lemerle, that illustrates the surprisingly close and amicable relationship between the Byzantine city and its "barbarian" neighbours.

A large-scale manhunt was launched against Perboundos, and fears of an imminent Slavic move on Thessalonica led the emperor to send a swift dromon to warn the city and instruct its leaders to take precautions and stockpile food in case of a siege.

[19] This Slavic league blockaded Thessalonica by land and raided its environs, with each tribe being assigned a specific area: the Strymonitai attacked from the east and north, the Rhynchinoi from the south, and the Sagoudatai from the west.

[20][21] The historian Florin Curta comments that the Slavs "appear as better organized than in any of the preceding sieges, with an army of special units of archers and warriors armed with slings, spears, shields, and swords".

[22][23] The situation was made worse by the city's authorities, who allowed the grain hoarded in the granaries, following the emperor's instructions, to be sold to foreign ships in the harbour, at a rate of a nomisma for seven modii, just one day before the start of the blockade.

[29][30] According to the account of the Miracles, the first miraculous intervention of Saint Demetrius caused the Strymonitai to halt and turn back once they were three miles from the city walls; the reasons for this defection are unknown, but it effectively left only the Rhynchinoi and the Sagoudatai to carry the brunt of the fighting.

[31] Due to the hagiographic nature of the Miracles, and the use of common literary topoi, gleaning details about the fighting from the account is difficult; certainly the siege engines provided by the Drougoubitai are not mentioned as playing any particular role in the events.

Most notably he is recorded as appearing in person, on foot and bearing a cudgel, to repel an attack by the Drougoubitai against a postern at a place called Arktos—an event which some modern commentators have interpreted as indicating that the Slavs penetrated into the city.

Lemerle remarks on the surprising absence of similar orders to the navy, given the recent piratical activity of the Slavs, but considers that the expedition was aimed at resolving the problem at its root, striking at the habitats of the tribes responsible.

[36][37] The emperor also sent a grain fleet under strong escort by warships, carrying 60,000 measures of wheat for the city, in what Lemerle considers an eloquent testament of renewed ability of the Byzantine central government to intervene decisively in the Balkans after the Arab danger had passed.

[39] Hélène Antoniades-Bibicou and Halina Evert-Kappesova suggested a different reconstruction, with the arrest of Perboundos occurring in 644, followed by the two-year siege of Thessalonica, with the great Slavic assault on the "fifth indiction" in 647, followed by an imperial campaign against the Strymonitai in 648/649.

[43][44] The chronology accepted today by most scholars[45] is that established by Paul Lemerle in his critical edition of the Miracles, which relies on a number of factors: the great time elapsed since the previous Slavic sieges, as inferred from the narrative, points to an exclusion of earlier dates; the emperor reigning during the siege was the same as that reigning when the account was compiled, which excludes Justinian II, since his arrival in person in Thessalonica would have been mentioned by the author; and the emperor's preoccupation with a conflict with the Arabs, which removes 662, when the Arabs were in peace with Byzantium due to the First Fitna.

This leaves 676/677, when the Byzantines under Constantine IV (r. 668–685) were confronted with the huge attack launched by the Umayyad Caliphate in 671/672, that culminated in the Siege of Constantinople in 674–678, as the only "fifth indiction" that matches all the facts described in the source.

[46] The reconstructed chronology that Lemerle suggested places the arrest and execution of Perboundos sometime in early 676, with the Slavic alliance starting the siege in summer 676 and culminating in the great assault against Thessalonica in July 677.