The siege of Bilär was a battle for the capital city of the Volga Bulgaria between the Volga Bulgars and the Mongols. It took place in autumn 1236 and lasted for 45 days. It ended with the total destruction of Bilär and the massacre of its population, estimated several dozen thousands. After the battle of Samara Bend the Bolghars renovated all fortification of Bilär, the city was encircled with the third 11-kilometre-long wall of stone and wood. However, after the Mongols besieged the city, it withstood the siege only for 45 days.