Kaloyan of Bulgaria
Kaloyan of Bulgaria occupied the region between the rivers Cerna and the Olt around 1199. The Kingdom of Hungary was also expanding southwards over the Carpathian Mountains in the early 13th century, which gave rise to conflicts between the two countries. The Cuman tribes dwelling to the east of the Olt as far as the river Siret agreed to pay a yearly tribute to the kings of Hungary in early 1227. The Hungarians captured the Bulgarian fortress of Severin during a military campaign against Bulgaria in 1231.