Battle of Rusion The battle of Rusion ( ) occurred in the winter of 1206 near the fortress of Rusion ( Ruskoy , contemporary Turkey ) between the armies of the Bulgarian Empire and the Latin Empire of Byzantium . The Bulgarians scored a major victory . Origins of the conflict . The stunning victory in the battle of Adrianople was followed by other Bulgarian victories at Serres and Plovdiv . The Latin Empire suffered heavy casualties and in the fall of 1205 the Crusaders tried to regroup and reorganize the remains of their army . Their main forces consisted of 140 knights and several thousand soldiers based in Rusion . This army was led by Thierry de Termond and Thierry de Loos who were among the most notable nobles of the Latin Empire of Constantinople . The battle . In mid January 1206 the Bulgarian army marched southwards . Part of the troops besieged Adrianople and the others under the personal command of Kaloyan headed to Rusion . According to his battle plan he had to force the Latins to go out of the fortress . For that purpose a small company of Cuman raiders seized a small and insignificant castle in the vicinity of Rusion . Kaloyan presumed on the ignorance and lack of discipline of the Crusaders . The maneuver worked - in the evening of 30 January the Crusaders marched from the city gates . Thierry de Loos was recalled to Constantinople and now Thierry de Termont who was known as a recklessly brave man remained in charge . The Byzantine historian Niketas Choniates wrote that his troops were the bravest in the whole Latin army . Around 120 knight s and many cavalrymen set off from Rusion and rode the whole night . In the morning of 31 January they reached the castle but found it was deserted by the Bulgarians and headed back to Rusion . In the meantime 7 , 000 Bulgarians went round the Crusaders and took positions at 7 km before the walls of Rusion . The defenders of the fortress were few and could only watch from the towers . From there they could see the approaching Latin army divided into four detachments . The advanced guard was led by Charles de Fren , then followed the troops of Termont and the detachment of Andres Deboas and Jean de Choasy who were the first knights to climb the walls of Constantinople in 1204 . The last detachment was under the command of Vilen de Loos , brother of Thierry de Loos . The battle began in the rear - guard . The detachment of Vilen de Loos was attacked by another Bulgarian force and despite the desperate resistance was routed . The survivors mixed up with the troops in front of them and soon the next two Crusader detachments were defeated . The battle was fought while the armies were on the march and the masses of fighting soldiers were slowly moving to Rusion . At about 2 km from the fortress the Crusader battle formation finally collapsed under the Bulgarian assaults from both sides . The knights fought bravely and most of them perished . Only ten of the 120 knights managed to reach Rusion . Thousands of ordinary soldiers were killed in the battle or captured . All Crusader commanders including Thierry de Termond perished . The remains of the crushed army abandoned Rusion and sought refuge to the nearby town of Rodosto . Further developments . Rodosto was well - fortified town with a large garrison of Venetians consolidated by the survivors from Rusion and a company of 2 , 000 men who arrived later . However , when Kaloyan arrived the defenders panicked and after a short battle were completely defeated and Rodosto was looted . Many more towns were soon seized such as Perint , Chorlu , Arkadiopolis , Messina , Daonion . The Bulgarians besieged the important town of Didymoteicho which was taken in the following year . Aftermath . In the whole military operation the Crusaders lost more than 200 knights , many thousands of soldiers and several Venetian garrisons were completely annihilated . The new Emperor of the Latin Empire Henry of Flanders had to ask the French King for another 600 knights and 10 , 000 soldiers . Geoffrey of Villehardouin compared the defeat with the disaster at Adrianople . However , the Crusaders were lucky - in 1207 Tsar Kaloyan was killed during the siege of Thessaloniki and the new Emperor Boril who was an usurper needed time to enforce his authority .