Battle of PhilippopolisPlovdiv, Bulgaria
In the spring of 1208, the Bulgarian army invaded Thrace and defeated the Crusaders near Beroe (modern Stara Zagora). Inspired, Boril marched southward and, on 30 June 1208, he encountered the main Latin army. Boril had between 27,000 and 30,000 soldiers, of which 7000 mobile Cuman cavalry, very successful in the Adrianople's battle. The number of Latin army is also around 30,000 fighters total, including several hundred knights. 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. The knights, however, had learned the bitter lesson from Adrianople and did not repeat the same mistake. Instead, they organized a trap and attacked the detachment which was personally commanded by the Tsar, who had only 1,600 men and could not withstand the assault. Boril fled and the whole Bulgarian army pulled back.
The Bulgarians knew that the enemy would not chase them into the mountains so they retreated towards one of the eastern passes of the Balkan Mountains, Turia. The Crusaders who followed the Bulgarian army were attacked in a hilly country near the contemporary village of Zelenikovo by the Bulgarian rear guard and, after a bitter fight, were defeated. 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. The Crusaders then retreated to Philippopolis.