The battle of Katasyrtai occurred in the fall of 917, shortly after the striking Bulgarian triumph at Achelous near the village of the same name close to the Byzantine capital Constantinople, (now Istanbul). The result was a Bulgarian victory. The last Byzantine military forces were literally destroyed and the way to Constantinople was opened, but the Serbs rebelled to the west and the Bulgarians decided to secure their rear before the final assault of the Byzantine capital which gave the enemy precious time to recover.