Kaloyan defeated the Latins at Adrianople in 1205.
The Battle of Adrianople took place on April 14, 1205, near the Thracian city now known as Edirne, Turkey. Kaloyan, ruler of the Second Bulgarian Empire, supported Greek rebels resisting the newly created Latin Empire, which had been established after the Fourth Crusade captured Constantinople in 1204.
The Latin army was led by Emperor Baldwin I of Constantinople. Kaloyan’s forces included Bulgarians, Vlachs, and allied Cuman cavalry. The Cumans repeatedly feigned retreat, drawing Latin knights away from their camp and into marshy ground prepared with concealed obstacles. The Bulgarians then surrounded and crushed the heavily armored cavalry. Baldwin was captured and later died in Bulgarian captivity.
A common mix-up is confusing Kaloyan with Basil II, the earlier Bulgarian-slaying Byzantine emperor, or with Ivan Asen II, who ruled Bulgaria later. Adrianople was a major early defeat for the Latin Empire and showed that the crusaders’ conquest of Constantinople had not secured their control of the Balkans.