During the Mongol invasion of Europe, Mongol tumens led by Batu Khan and Kadan invaded Serbia and then Bulgaria in the spring of 1242 after defeating the Hungarians at the battle of Mohi and ravaging the Hungarian regions of Croatia, Dalmatia and Bosnia.
Initially, the troops of Kadan moved south along the Adriatic Sea into Serbian territory. Then, turning east, it crossed the centre of the country—plundering as it went—and entered Bulgaria, where it was joined by the rest of the army under Batu. The campaigning in Bulgaria probably happened mainly in the north, where archaeology yields evidence of destruction from this period. The Mongols did, however, cross Bulgaria to attack the Latin Empire to its south before withdrawing completely. Bulgaria was forced to pay tribute to the Mongols, and this continued thereafter.
Background
Relations between Hungary and Serbia were poor on the eve of the Mongol invasion. The Serbian king, Stefan Vladislav, had married Beloslava, daughter of Tsar Ivan Asen II of Bulgaria, in 1234 in an effort to form an anti-Hungarian alliance. By the time of the Mongol invasion, however, there were good relations between Hungary and Bulgaria. The Bulgarian tsar, the child Kaliman I, was a nephew of the Hungarian king, Béla IV, being the son of Béla's sister, Anna Maria, and Ivan Asen II. Around 1240, facing the threat of Mongol invasion, the Hungarians, Bulgarians and Cumans may have entered into an alliance, as evidenced by the presence in that year of a Bulgarian emissary at Béla IV's court.
One of the reasons for the Mongol invasion of Hungary was that Béla IV had given shelter to the Cumans when they fled the Mongol conquest of their land in 1239. After the Cuman leader, Köten, was assassinated by Hungarians opposed to Béla's policy on 17 March 1241, a large number of Cumans devastated the Hungarian countryside while retreating into Bulgaria, where they were again granted shelter. A separate group of Cumans entered Bulgaria about the same time, crossing the Black Sea after the Mongol conquest of Cumania, having arranged for their settlement with Ivan Asen. This is recorded by Ibn Taghribirdi, a 15th-century writer relying on the lost work of Izz al-Din ibn Shaddad, himself a Syrian writing in exile from Egypt after the Mongol conquest of Syria. Izz al-Din's source was the eyewitness Badr al-Din Baysari, himself a Cuman whose family fled to Bulgaria. The future sultan of Egypt, Baibars, born in 1227 or 1228, was among those who fled to Bulgaria from the Mongols. According to Ibn Taghribirdi, the Bulgarians later turned on these Cumans. Baysari and Baibars were captured and sold into slavery in Rum. The Cumans of Köten, on the other hand, seem to have integrated themselves into the Bulgarian aristocracy.
The decision by the Mongols to attack Bulgaria with all their forces may have had the same motive as the initial attack on Hungary: to punish the Bulgarians for giving aid to the Mongols' enemies.
Bulgaria in 1242 encompassed the area north of the Balkan Mountains as far as the Lower Danube. Its population was ethnically mixed, consisting of Slavic-speaking Bulgarians and Romance-speaking Vlachs. Some contemporaries called the area Vlachia. The nomadic Cumans also settled in this region at that time. The ruling dynasty since 1185 was the Asenids. Their ethnic origins are disputed, but most likely they were Cumans who became Romanized in the 12th century and Slavicized in the 13th.
In dealing with the Mongol invasions, writers also had to distinguish between Bulgaria on the Danube and the distant Bulgaria on the Volga, which they called, respectively, "Little (or Lesser) Bulgaria" (Bulgaria minor) and "Great (or Greater) Bulgaria" (Bulgaria maior or magna Bulgaria).
Serbia
When the Mongol commander Kadan withdrew from the invasion of Hungary, he entered Bosnia in late March or early April 1242. Although nominally under Hungarian suzerainty, part of Bosnia had been occupied by Hungarian crusaders opposed to the Bosnian Church while the remainder was under the control of Ban Matej Ninoslav. The passing-through of the Mongols forced the Hungarians to evacuate the territory and allowed Ninoslav to resume control of the whole of Bosnia.