The new Emperor had to cope with the supporters of the country's legitimate heir Ivan Asen II who was juvenile at that time.

Boril tried to apply the same tactics used by Kaloyan at Adrianople - the mounted archers harassed the Crusaders trying to stretch their line to lead them towards the main Bulgarian forces.

However, their formation did not collapse as the main Latin forces arrived and the battle continued for a very long time until the Bulgarians retreated to the north after the bulk of their army had safely passed through the mountains.

To compensate, Boril had to arrange an alliance with his brother Strez who ruled in Prosek - he had received the high title sevastokrator and the right to govern his lands freely.

After that failure Boril reorientated his policy and the two Empires settled peace after the marriage of Kaloyan's daughter Maria of Bulgaria and the Latin Emperor Henry.