Avar-Persian Siege of Constantinople

Timeline

1. 626Walls of Constantinople · ConstantinopleThe Avar khagan advanced from Thrace with tens of thousands of cavalry and Slavic vassals, while Persian forces moved north through the Bosphorus, attempting a combined land-sea assault. Emperor Heraclius was then organizing a counteroffensive against Persia in Anatolia, and the capital's defense fell to the senate and the church jointly.
2. 626Hagia Sophia · ConstantinoplePatriarch Sergius led the people along the Theodosian Walls, processing day and night and holding religious ceremonies to boost morale. The garrison used the strong fortifications and the chain across the Golden Horn to withstand repeated Avar assaults on the walls.
3. 626Bosphorus · ConstantinopleThe Byzantine fleet defeated the Persian squadron in the strait, severing coordination between the Persian and Avar forces. Without naval support the Persians could not effectively join the siege, and the coalition's offensive stalled.
4. 626Constantinople · ConstantinopleWhen Byzantine reinforcements arrived by sea, the Avar coalition's supplies were cut and morale collapsed; the khagan withdrew north with his remnants. Constantinople was saved, greatly boosting imperial confidence and enabling Heraclius's counteroffensive against Persia the following year.