At the beginning of 1241 the Mongol army seized Kiev, then crossed the Carpathian mountains and invaded Poland. Roger Bacon in his Opus Majus writes that the Mokshas were in the vanguard of the Mongol army and took part in the capture of Lublin and Zawichost in Poland. Benedict Polone reports that the Mokshan army suffered serious losses during the capture of Sandomierz in February and Krakow in March of the same year. On 9 April 1241 the Mongol army defeated the allied Polish and German armies at the Battle of Legnica. It is believed King Puresh was slain in that battle. Shortly after that battle the Mokshan army declared to Batu that they refused to fight against Germans. According to reports by William Rubruck and Roger Bacon, the Mokshas had previously negotiated with the Germans and Bohemians regarding the possibility of joining their side in order to escape from their forced vassalage to Batu. It is known that Subutai ordered the punishment of the conspirators; thousands of Mokshas were put to death, but approximately a third escaped and returned to their homeland. Another third remained in the vanguard of the Mongol army and marched into Hungary through the Verecke Pass in March 1242, according to the Hungarian bishop Stephan II and Matthew of Paris.