Kaloyan decided to take vengeance of the townspeople of Philippopolis, who had voluntarily cooperated with the crusaders. With the assistance of the local Paulicians, he seized the town and ordered the murder of the most prominent burghers. The commoners were delivered in chains to Vlachia (a loosely defined territory, located to the south of the lower Danube). He returned to Tarnovo after a riot had broken out against him in the second half of 1205 or early 1206. He "subjected the rebels to harsh punishments and novel methods of execution", according to Choniates.

He again invaded Thrace in January 1206. The great victory in the battle of Adrianople was followed by other Bulgarian victories at Serres and Plovdiv. The Latin Empire suffered heavy casualties and in the fall of 1205 the Crusaders tried to regroup and reorganize the remains of their army. Their main forces consisted of 140 knights and several thousand soldiers based in Rusion. He captured Rousion and massacred its Latin garrison. He then destroyed most of the fortresses along the Via Egnatia, as far as Athira. In the whole military operation the Crusaders lost more than 200 knights, many thousands of soldiers and several Venetian garrisons were completely annihilated.