Siege of Bilär
1236 CE.
Shown on the map at 54.985°, 50.398°.
The siege of Bilär was a battle for the capital city of Volga Bulgaria, between the Volga Bulgars and the Mongols. It took place in the autumn of 1236 and lasted 45 days. It ended with the destruction of Bilär and the massacre of its population, estimated at several dozen thousand. After the Battle of Samara Bend, the Bolghars renovated Bilär's fortifications. The third 11-kilometre-long wall of stone and wood encircled the city. However, after the Mongols besieged the city, it withstood the siege only for 45 days. By the materials uncovered by archaeological excavations, the city was burnt after falling, and the unburied remains of its population were found all over Bilär.
Text from the Wikipedia article Siege of Bilär, licensed CC BY-SA 4.0.