Battle of Makryplagi
1263 CE.
Shown on the map at 37.170°, 22.000°.
The Battle of Makryplagi or Makry Plagi was fought between the forces of the Byzantine Empire, and the Latin Principality of Achaea. The Byzantines had been weakened and demoralized by the defection of their numerous Turkish mercenaries to the Achaeans. At Makryplagi, the Byzantines suffered a heavy defeat, which together with their defeat at the Battle of Prinitza the previous year ended their attempted reconquest of the Morea.
Text from the Wikipedia article Battle of Makryplagi, licensed CC BY-SA 4.0.