Byzantine – Mongol alliance A Byzantine – Mongol alliance occurred during the end of the 13th and the beginning of the 14th century between the Byzantine Empire and the Mongol Empire . Byzantium actually tried to maintain friendly relations with both the Golden Horde and the Ilkhanate realms , who were often at war with each other . The alliance involved numerous exchanges of presents , military collaboration and marital links , but dissolved in the middle of the 14th century . Diplomatic overtures . Soon after the Battle of Kose Dag in 1243 , the Empire of Trebizond surrendered to the Mongol Empire while the court of Nicaea put its fortresses in order . In the early 1250s , the Latin emperor of Constantinople Baldwin II sent an embassy to Mongolia in the person of the knight Baudoin de Hainaut , who , following his return , met in Constantinople with the departing William of Rubruck . William of Rubruck also noted that he met an envoy of John III Doukas Vatatzes , emperor of Nicaea , at the court of Möngke Khan in circa 1253 . Alliance under Michael VIII ( 1263 – 1282 ) . Emperor Michael VIII Palaiologos , after re - establishing Byzantine Imperial rule , established an alliance with the Mongols , who themselves were highly favourable to Christianity , many of them being Nestorian Christian s . He signed a treaty in 1263 with the Mongol Khan of the Kipchak ( the Golden Horde ) , and he married two of his daughters ( conceived through a mistress , a Diplovatatzina ) to Mongol kings : Euphrosyne Palaiologina , who married Nogai Khan of the Golden Horde , and Maria Palaiologina , who married Abaqa Khan of Ilkhan id Persia . According to a 1267 letter by Pope Clement IV from Viterbo , Abaqa had agreed to combine forces with his father - in - law Michael VIII to help the Latins in the Holy Land , in preparation for the Eighth Crusade ( the second of Louis IX ) : In 1265 Berke Khan sent the Golden Horde army under Noghai to Thrace , prompting to force the Byzantine to release the Mamluk envoy and the former Seljuk Sultan Kaykaus II . According to Egyptian sources , Michael agreed to send fabric s to the Mongol Khan in Russia . When Michael realized the importance of the Mongols and became an ally of Noghai , he used his help to defend himself against Bulgaria when it tried to attack the Byzantine Empire in 1273 and 1279 . A group of 4 , 000 Mongol soldiers were dispatched to Constantinople in 1282 , just before the death of Michael , to fight against the despot of Thessaly . Alliance under Andronikos II ( 1282 – 1328 ) . After 1295 , Andronikos II offered Ghazan a marital alliance , in exchange for Mongol help to fight against the Turcomans at the Oriental frontier of the Byzantine Empire . Ghazan accepted the offer and promised to stop the incursions . The death of Ghazan in 1308 was mourned by the Byzantines . This alliance would continue under Ghazan ' s successor , Oljeitu . In 1305 Ilkhan Oljeitu promised Andronicus II 40 , 000 men , and in 1308 dispatched 30 , 000 men to recover many Byzantine towns in Bithynia . Andronicus II gave daughters in marriage to Toqto ' a , as well as his successor Uzbek ( 1312 – 1341 ) , but relations turned sour at the end of Andonicus ' s reign and the Mongols mounted raids on Thrace between 1320 to 1324 , until the Byzantine port of Vicina Macaria was occupied by the Mongols . End of friendly relations . Under Andronikos III relations seem to have turned even more conflictual . In 1341 , the Mongols planned to attack Constantinople , and Andronikos III had to send an embassy to stop the attack .