Using the migration of the Cumans as their "casus belli", the Mongols continued west, raiding Poland and Hungary, which culminated in Mongol victories at the battles of Legnica and Mohi. In 1241, however, Ögedei Khan died in the Mongolian homeland. Batu turned back from his siege of Vienna but did not return to Mongolia, rather opting to stay at the Volga River. His brother Orda returned to take part in the succession. The Mongol armies would never again travel so far west. In 1242, after retreating through Hungary, destroying Pest in the process, and subjugating Bulgaria, Batu established his capital at Sarai, commanding the lower stretch of the Volga River, on the site of the Khazar capital of Atil. Shortly before that, the younger brother of Batu and Orda, Shiban, was given his own enormous "ulus" east of the Ural Mountains along the Ob and Irtysh Rivers.