Béla and his family, including Stephen, fled to Zagreb after the Mongols had annihilated the royal army in the Battle of Mohi on 11 April 1241.
Béla dan keluarganya, termasuk István, melarikan diri ke Zagreb setelah Suku Mongol memusnahkan pasukan kerajaan di dalam Pertempuran Mohi pada tanggal 11 April 1241.