Battle of Ray
811 CE.
Shown on the map at 35.583°, 51.433°.
This Battle of Rayy (one among many) was fought on May 1, 811 AD as part of an Abbasid civil war (the "Fourth Fitna") between the two half-brothers, al-Amin and al-Ma'mun.
Text from the Wikipedia article Battle of Ray (811), licensed CC BY-SA 4.0.