departure Béla lost his most valuable allies. He could muster an army of less than 60,000 against the invaders. The royal army was ill-prepared and its commanders—the barons alienated by Béla's policy—"would have liked the king to be defeated so that they would then be dearer to him", according to Roger of Torre Maggiore's account. The Hungarian army was virtually annihilated in the Battle of Mohi on the Sajó River on 11 April 1241. A great number of Hungarian lords, prelates and noblemen were killed, and Béla himself narrowly escaped from the battlefield. He fled through Nyitra to Pressburg (Nitra and Bratislava in Slovakia). The triumphant Mongols occupied and ravaged most lands to the east of the Danube River by the end of June. Upon Duke Frederick II of Austria's invitation, Béla went to Hainburg an der Donau. However, instead of helping Béla, the Duke forced him to cede three counties (most probably Locsmánd, Pozsony, and Sopron). From Hainburg, Béla fled to Zagreb and sent letters to Pope Gregory IX, Emperor Frederick II, King Louis IX of France and other Western European monarchs, urging them to send reinforcements to Hungary. In the hope of military assistance, he even accepted Emperor Frederick II's suzerainty in June. The Pope declared a Crusade against the Mongols, but no reinforcements arrived. The Mongols crossed the frozen Danube early in 1242. A Mongol detachment under the command of Kadan, a son of Great Khan Ögödei, chased Béla from town to town in Dalmatia. Béla took refugee in the well-fortified Trogir. Before Kadan laid siege to the town in March, news arrived of the Great Khan's death. Batu Khan wanted to attend at the election of Ögödei's successor with sufficient troops and ordered the withdrawal of all Mongol forces. Béla, who was grateful to Trogir, granted it lands near Split, causing a lasting conflict between the two Dalmatian towns. "Second Founder of the State" (1242–61) Upon his return to Hungary in May 1242, Béla found a country in ruins. Devastation was especially heavy in the plains east of the Danube where at least half of the villages were depopulated. The Mongols had destroyed most traditional centers of administration, which were defended by earth-and-timber walls. Only well-fortified places, such as Esztergom, Székesfehérvár and the Pannonhalma Abbey, had successfully resisted siege. A severe famine followed in 1242 and 1243. Preparation for a new Mongol invasion was the central