To distract his attention the Byzantines decided to strike in eastern direction. They assembled the Eastern army under its commander Alexios Gidos and the Western army under its Domestic Basil Vatatzes to stop the dangerous rise of Bulgarian power. Near Arcadiopolis in Eastern Thrace they met the Bulgarian army. After a fierce battle the Byzantine armies were annihilated. Most of Gidos's troops perished and he had to flee for his life, while the Western army was fully slaughtered and Basil Vatatzes was killed on the battlefield.