Devastation of Hungary

During the summer and autumn of 1241, most of the Mongol forces were resting on the Hungarian Plain. In late March, 1242, they began to withdraw. The most common reason given for this withdrawal is the Great Khan Ögedei's death on December 11, 1241, which supposedly forced the Mongols to retreat to Mongolia so that the princes of the blood could be present for the election of a new great khan. 

The true reasons for the Mongol withdrawal are not fully known, but numerous plausible explanations exist. Regardless of their reasons, the Mongols had completely withdrawn from Central Europe by mid-1242, though they still launched military operations in the west at this time, most notably the 1241–1243 Mongol invasion of Anatolia.

The effects of the Mongol invasion were tremendous in the Kingdom of Hungary. The worst damage was incurred in the plains regions, where 50-80% of settlements were destroyed. The combination of massacres perpetrated by the Mongols, the famines induced by their foraging, and the simultaneous devastation of the countryside by the fleeing Cumans resulted in an estimated loss of 15–25% of Hungary's population, some 300,000–500,000 people in total. The only places that held in the face of Mongol assaults were approximately eighty fortified places, including all of the few stone castles in the kingdom. Among these places were Esztergom, Székesfehérvár, and the Pannonhalma Archabbey. However, these places were relatively few; a German chronicler in 1241 noted that Hungary "had almost no city protected by strong walls or fortresses", so the majority of settled areas were extremely vulnerable.