Siege of Manzikert
1054 CE.
Shown on the map at 39.000°, 32.000°.
The Siege of Manzikert in 1054 was a successful defence of the city of Manzikert by Byzantine forces under Basil Apokapes, against the Seljuks under Tughril I.
Text from the Wikipedia article Siege of Manzikert (1054), licensed CC BY-SA 4.0.