After the death of his uncle Kaloyan in 1207, Ivan Asen's cousin, Boril, usurped the throne and forced him to flee to the Russian principality of Galicia-Volhynia
The return of Andrew II of Hungary from the Fifth Crusade in 1218 provides an opportunity to establish a marriage alliance and to obtain (probably in 1221) the return of the disputed territories around Belgrade on the Danube as th
