Principality of Halych
Béla set up a defensive alliance against the Mongols. He married three of his daughters to princes whose countries were also threatened by the Mongols. Rostislav Mikhailovich, a pretender to the Principality of Halych, was the first to marry, in 1243, one of Béla's daughters, Anna. Béla supported his son-in-law to invade Halych in 1245, but Rostislav's opponent, Daniil Romanovich repulsed their attack.