During the First Mongol invasion of Hungary, Matthias and his deputy, archdeacon Albert gathered their army in Esztergom and joined Duke Coloman's troops, marching together to Pest. In the Battle of Mohi on 11 April 1241, Matthias personally led his troops, when fell with commander Archbishop Ugrin Csák and majority of the bishops (for instance, Reynold of Transylvania and Jacob of Nyitra were among them) as they were leading troops against Batu Khan. According to "magister" Roger, his body was never found.