The Hungarians had first learned about the Mongol threat in 1229, when King Andrew II granted asylum to some fleeing Russian boyars. Some Magyars (Hungarians), left behind during the main migration to the Pannonian basin, still lived on the banks of the upper Volga (it is believed by some that the descendants of this group are the modern-day Bashkirs, although this people now speaks a Turkic language, not Magyar).

In 1237 a Dominican friar, Julianus, set off on an expedition to lead them back, and was sent back to King Béla with a letter from Batu Khan. In this letter, Batu called upon the Hungarian king to surrender his kingdom unconditionally to the Tatar forces or face complete destruction. Béla did not reply, and two more messages were later delivered to Hungary. The first, in 1239, was sent by the defeated Cuman tribes, who asked for and received asylum in Hungary. The second was sent in February 1241 from Poland which was facing an invasion from another Mongol force.

Five separate Mongol armies invaded Hungary in 1241. The main army under Batu and Subutai crossed through the Verecke Pass. The army of Qadan and Büri crossed through the Tihuța Pass. Two smaller forces under Böchek and the noyan Bogutai entered Hungary from the southeast. The army that had invaded Poland under Orda and Baidar invaded Hungary from the northwest.