The Bulgarian army had already done the impossible once that autumn. At Achelous on 20 August 917, Tsar Simeon I shattered the main Byzantine forces in one of the most decisive defeats in the empire's long history. Now his soldiers were marching south toward Constantinople itself, and the only man standing between them and the greatest city in the Christian world was a general named Leo Phokas—a survivor of Achelous who had fled by sea and was now scraping together whatever troops remained within the capital's walls. What happened next, in the dark outside a village called Katasyrtai just beyond Constantinople's gates, would bring the Byzantine Empire to the edge of collapse.
The year 917 had been one of desperate Byzantine preparation. Constantinople knew that Simeon I of Bulgaria—educated in the imperial city, schooled in Greek rhetoric and Orthodox theology, and now its most dangerous enemy—was seeking a decisive confrontation. The Byzantines assembled what chroniclers describe as an enormous army and attempted to build a coalition of allies to hem Bulgaria in from multiple directions. The coalition failed. Simeon moved faster than their diplomacy. When the main Byzantine force met the Bulgarian army at the Battle of Achelous near the Black Sea coast in the early autumn, the result was catastrophic. The Byzantine military, the professional core that had defended the empire for generations, was shattered in a single afternoon.
Leo Phokas reached Constantinople ahead of the Bulgarian advance, sailing along the coast after surviving the rout at Achelous. Inside the city, he gathered what forces he could—garrison troops, remnants who had straggled back, soldiers scraped from whatever units remained. It was not much, but he had no choice: if the Bulgarians reached the Theodosian Walls without opposition, there was no guarantee those walls alone could hold. He led his men out beyond the city to the village of Katasyrtai, a settlement near the capital on the western approach, and made his stand. The Bulgarians arrived, and the two sides fought through the night. When dawn came, the Byzantine force had been completely routed. The men who had come to be the empire's last defenders were gone.
After Katasyrtai, the road to Constantinople stood open. Simeon's army had destroyed, in succession, the main Byzantine field force at Achelous and then the last reserve at Katasyrtai. Nothing capable of meeting them in the field remained. The Bulgarian soldiers who had marched south from the Balkan passes had accomplished something no enemy had managed in centuries: they had left Byzantium militarily hollow. Constantinople itself—ringed by the impregnable triple Theodosian Walls, fed by the sea—was another matter. But the empire's capacity to fight outside those walls had ceased to exist. The Bulgarians stood on the threshold of the city their tsar had dreamed of ruling.
What saved Constantinople was not a Byzantine victory but a Bulgarian problem. To the west, the Serbs rose in rebellion. Simeon had to turn his attention away from the golden prize just ahead and secure his rear before the final assault could be mounted. That decision—forced on him by the complexity of Balkan politics—gave the Byzantines something they had not earned: time. Time to mourn the dead of Achelous and Katasyrtai. Time to rebuild. Time to find new strategies, new alliances, new ways to survive against an enemy who had proven he could beat them in open battle. The soldiers who fell at Katasyrtai in the autumn of 917 never knew how narrow the margin was—or that their sacrifice, and the Serbian rising that followed, would preserve the empire for another five centuries.
The village of Katasyrtai stood just west of Constantinople, in the area now occupied by the western districts of modern Istanbul near the ancient Theodosian Walls. Coordinates: 41.03°N, 28.89°E. From cruising altitude approaching Istanbul from the northwest, the Sea of Marmara and the Bosporus strait are visible to the east, with the peninsula of the old city—ancient Constantinople—clearly defined by water on three sides. The nearest major airport is Istanbul Airport (LTFM), approximately 20 km northwest. Approach along the E80 corridor provides a view of the surviving stretches of the Theodosian Walls, still standing after more than 1,600 years, that Leo Phokas and his men fought to protect.