Kaloyan took advantage of the disintegration of the Byzantine Empire after the fall of Constantinople to the Crusaders (or "Latins") in 1204. He captured fortresses in Macedonia and Thrace and supported the local population's riots against the crusaders. He defeated Baldwin I, Latin emperor of Constantinople, in the Battle of Adrianople on 14April 1205. Baldwin was captured; he died in Kaloyan's prison. He launched new campaigns against the crusaders and captured or destroyed dozens of their fortresses. He was thereafter known as Kaloyan the "Romanslayer", because his troops murdered or captured thousands of Byzantines. He died under mysterious circumstances during the siege of Thessalonica in1207.