On the eve of the Mongol invasion of Hungary in 1241 in order to defend the country as successfully as possible the Hungarian King Bela IV welcomed Cumans to his state (1239). They had previously clashed with the Mongols in the area of the Black Sea region of steppes and they were threatened by them. However, after the murder of their khan Kotyan, Cumans left Hungary in 1241 and found refuge in neighboring Bulgaria. During the retreat southward they devastated the Hungarian border area of Srem (Marchia) and shortly after that armed Mongols themselves passed through this land. On the basis of the analysis of known and indirect sources still not considered in historiography in the context of this topic and based on the views of historiography...