During 1303–1304 Tsar Theodore Svetoslav of Bulgaria invaded Eastern Thrace. He sought revenge for the Tatar attacks on the state in the previous 20 years. The traitors were punished first, including Patriarch Joachim III, who was found guilty of helping the enemies of the crown. Then the tsar turned to Byzantium, which had inspired the Tatar invasions and had managed to conquer many Bulgarian fortresses in Thrace. In 1303, his army marched southwards and regained many towns. In the following year the Byzantines counter-attacked and the two armies met near the Skafida river. Michael IX at this time was engaged in a war with the rebellious Catalan Company, whose leader, Roger de Flor, refused to fight the Bulgarians if Michael IX and his father didn't pay him the agreed sum of money. 

At the beginning of the battle, Michael IX, who fought bravely in the forefront, had an advantage over the enemy. He forced the Bulgarians to retreat along the road to Apolonia, but he was unable to keep his own soldiers heated up in pursuit. Between the Byzantines and the fleeing Bulgarians, there was the deep and very turbulent Skafida river, with the only bridge across which was damaged by the Bulgarians before the battle. When the Byzantine soldiers in a large crowd tried to cross the bridge, it collapsed. Many of the soldiers drowned, the rest began to panic. At that moment, the Bulgarians returned to the bridge and decided the outcome of the battle, snatching victory from the enemies.