Battle of Anchialus
708 CE.
Shown on the map at 42.550°, 27.650°.
The Battle of Anchialus (Bulgarian: Битката при Анхиало) (Medieval Greek: Μάχη του Αγχίαλου) occurred in 708 near the modern-day town of Pomorie, Bulgaria
Text from the Wikipedia article Battle of Anchialus (708), licensed CC BY-SA 4.0.