Mongol invasion of the Latin Empire

There is only one primary source that explicitly mentions a Mongol raid into the Latin Empire: the anonymous Austrian Chronicle completed about 1327.

[1] According to the Austrian chronicles:[2] Tatars and Cumans, meeting no resistance or opposition, withdrew from Hungary with an endless booty of gold and silver, garments and animals, leading many captives of both sexes to the scandal of the Christians.

[3] A brief account in the Chronography of the Syriac prelate Bar Hebraeus (died 1286) must refer to the Mongol invasions of Bulgaria and Thrace in 1242, although it is mis-dated to 1232: And the Khan continued to wax strong.

[4] This passage seems to confirm that the Mongol armies in Bulgaria, which were under the overall command of Batu, attacked in the direction of Constantinople and were defeated at some point either by the Bulgars or the Latins.

[4][5] John of Garland in his epic poem On the Triumph of the Church, which he completed about 1252 while teaching at the University of Paris, lists the victims of the expansion of the Mongol empire: The avenger arriving from the East mows down everything he encounters And subdues the West with his sword.

Prince Geoffrey II of Achaea, who was married to Baldwin's sister Agnes, even sailed with an army to Constantinople on the basis of this rumour, perhaps hoping to seize the throne.

It definitely included Thrace, which was part of the Latin Empire and bordered Bulgaria, which makes it the likely location of the Mongol raids.

Peter Jackson suggests that Baldwin's initial victory may have come at the expense of these Cumans before the Mongol force arrived to defeat him.

In that event, he was likely forced to accept Mongol overlordship and to make annual tribute payments in return for release.

In 1253, he gave William of Rubruck, a Franciscan missionary, letters of recommendation for Sartaq, the son of Batu, khan of the Golden Horde.

The Byzantine emperor seems to have taken advantage of Baldwin's situation to attempt to retake Constantinople, albeit unsuccessfully, as reported in the chronicle of Martin da Canal.