Béla IV of Hungary was the only monarch in the thirteenth century to flee his own kingdom while his army was being slaughtered by an enemy that would soon vanish from the map. On the 11th of April 1241, the Mongol horde under Batu Khan shattered the Hungarian forces at the Battle of Mohi, killing thousands of nobles and prelates in a single afternoon. Béla himself escaped the carnage, only to be chased like a hunted animal from town to town, eventually seeking refuge in the coastal fortress of Trogir on the Adriatic Sea. He watched as his kingdom was reduced to a wasteland, with at least half of the villages in the eastern plains depopulated and traditional centers of administration destroyed by fire. The Mongols withdrew in March 1242 not because of Hungarian resistance, but because the Great Khan Ögödei had died, forcing Batu to return to the steppes for the succession. Béla returned to a country that had lost fifteen percent of its population to death and famine, a realm where the very foundations of royal authority had been erased by the invaders.
The Second Founder
In the wake of the Mongol withdrawal, Béla IV embarked on a reconstruction project so radical that it earned him the epithet of the second founder of the state. He abandoned the ancient royal prerogative to build and own castles, instead allowing barons and prelates to erect nearly one hundred new stone fortresses across the kingdom. This decision transformed the landscape of Hungary, turning the once open plains into a network of defensive strongholds that would define the country's military strategy for centuries. To replace the lost population, he granted special liberties to thousands of colonists from the Holy Roman Empire, Poland, and other neighboring regions, settling them in the depopulated lands. He even persuaded the Cumans, who had fled during the invasion, to return and resettle along the Tisza River. The most significant of his urban reforms was the relocation of the citizens of Pest to a hill on the opposite side of the Danube in 1248, creating the fortified town of Buda, which would become the most important commercial center in Hungary within two decades.The King of Cumania
Béla IV's relationship with the nomadic Cumans was a complex dance of necessity and betrayal that shaped the early years of his reign. In 1239, at least 40,000 Cumans fled the Mongol advance and demanded admission into Hungary, promising to convert to Christianity and fight the invaders. Béla accepted them, adopting the title of King of Cumania in 1233 to assert his suzerainty over their lands. However, the settlement of these masses of nomads in the plains along the Tisza River gave rise to constant conflicts with local villagers. The Cumans committed robberies and rapes, yet Béla rarely punished them because he needed their military support. This bias created deep enmity between the king and his Hungarian subjects, a tension that would explode into tragedy when the Cumans were massacred after the death of their leader, Köten. The mob in Pest, fearing collaboration with the enemy, slaughtered Köten's retinue, causing the Cumans to flee and destroy villages on their way to the Balkans, leaving Béla without his most valuable allies just as the Mongols returned.