Battle of Marcellae
792 CE.
Shown on the map at 42.638°, 26.896°.
The Battle of Marcellae (Bulgarian: Битката при Маркели; Greek: Μάχη των Μαρκελλών) was fought on the 20 July 792 between the forces of the Byzantine Empire, led by Constantine VI, and those of the First Bulgarian Empire under Kardam. The Byzantines were routed and forced to retreat to Constantinople. Fighting took place at Marcellae (Markeli), near the modern town of Karnobat in southeastern Bulgaria, the same site as an earlier battle in 756.
Text from the Wikipedia article Battle of Marcellae, licensed CC BY-SA 4.0.