Miracles of Saint Demetrius

The Miracles of Saint Demetrius, also known by the Latin title Miracula Sancti Demetrii, is a 7th-century collection of homilies, written in Greek, accounting the miracles performed by the patron saint of Thessalonica, Saint Demetrius. It is a unique work for the history of the city and the Balkans in general, especially in relation to the Slavic invasions of the late 6th and 7th centuries, which are otherwise neglected by contemporary sources.

The Miracles comprise two books. The first was compiled between ca. 610 and ca. 620 by John, Archbishop of Thessalonica, and the second was compiled in the 680s. The first book enumerates fifteen episodes of the Saint's intervention on behalf of Thessalonica, most of which occurred in the episcopate of John's predecessor, Eusebius, including outbreaks of plague and the siege of the city by the Sclaveni (proto-South Slavs) and Avars. These episodes were written in the form of homilies or sermons, to be publicly read to the city's populace in order to demonstrate the Saint's active presence and intercession on their behalf.

The second book differs considerably in style, and is closer to an actual historical account, with the unknown author being an eyewitness or using written annals or eyewitness testimonies for the events he is describing, i.e. the Slavic invasion and settlement of the Balkans, including a series of sieges of Thessalonica by the Slavs and the Avars, culminating in the great Slavic attack of ca. 677. Whereas in Book I John portrays the Slavs as generic barbarians, the unknown author of Book II is far more familiar with them and their tribal divisions, listing the several Slavic tribes that settled around the city and calling them "our neighbours". Due to its change in style and focus, the second book proved less popular than the first with copyists in the following centuries, and survives in only a single manuscript.

The Miracles are particularly valuable as a historical source. As the eminent scholar of the medieval Balkans, Dimitri Obolensky, writes, "in no other contemporary work will he find so much precise and first-hand information on the military organization and topography of Thessaloniki during one of the most dramatic centuries of its history; on the methods of warfare and the techniques of siege-craft used in the Balkan wars of the time; and on the strategy and tactics of the northern barbarians who, thrusting southward in successive waves down river valleys and across mountain passes, sought in the sixth and seventh centuries to gain a foothold on the warm Aegean coastland and to seize its commanding metropolis which always eluded their grasp. And there can be few documents stemming from the Christian world of the Middle Ages in which the belief held by the citizens of a beleaguered city that they stand under the supernatural protection of a heavenly patron is so vividly and poignantly expressed."

...
Wikipedia