The Third Battle of Serres

After the crushing victory over the Latins at Adrianople on 14 April 1205, the Bulgarians gained control of most of Thrace, except Constantinople, Rodosto and Selymbria. In June 1205, Tsar Kaloyan redirected operations south-west towards the Kingdom of Thessalonica, ruled by Boniface of Montferrat, a vassal of the Latin Empire. Leading a large regular army, he confronted the formidable fortress of Serres. During the battle, Boniface sent additional troops as reinforcements.

Kaloyan's troops defeated Boniface's forces defending Serres. Some reinforcement units were destroyed, while others withdrew. The Bulgarian ruler's armies then continued their campaign.