of the Sajó river in 1241 by the Mongols, Béla IV fled to today's Zagreb in Croatia. Batu sent a few tumens (roughly 20,000 men at arms) under Khadan in pursuit of Bela. The major objective was not the conquest but the capture of the Arpad king. The poorly fortified Zagreb was unable to resist the invasion and was destroyed, its cathedral burned by Mongols. In preparation for a second invasion, Gradec was granted a royal charter or Golden Bull of 1242 by King Béla IV, after which citizens of Zagreb engaged in building defensive walls and towers around their settlement. The Mongols' pursuit of Béla IV continued from Zagreb through Pannonia to Dalmatia. While in pursuit, the Mongols under the leadership of Kadan (Qadan) attacked Klis Fortress in Croatia in March 1242. Due to the strong fortifications of Klis, the Mongols dismounted and climbed over the walls using nearby cliffs. The defenders were able to inflict a number of casualties on the Mongols, which enraged the latter and caused them to fight hand to hand in the streets and gather a sizable amount of loot from houses. As soon as they learned that King Bela was elsewhere, they abandoned the attack and split off to attack Split and Trogir. The Mongols pursued Béla IV from town to town in Dalmatia, while Croatian nobility and Dalmatian towns such as Trogir and Rab helped Béla IV to escape. After being defeated by the Croatian soldiers, the Mongols retreated and Béla IV was awarded Croatian towns and nobility. Only the city of Split did not aid Béla IV in his escape from the Mongols. Some historians claim that the mountainous terrain of Croatian Dalmatia was fatal for the Mongols because of the great losses they suffered from Croat ambushes in mountain passes. In any case, though much of Croatia was plundered and destroyed, long-term occupation was unsuccessful. Saint Margaret (January 27, 1242 – January 18, 1271), a daughter of Béla IV and Maria Laskarina, was born in Klis Fortress during the Mongol invasion of Hungary-Croatia in 1242. Historians estimate that up to half of Hungary's two million population at that time were victims of the Mongol invasion of Europe. Invasion of German lands On 9 April 1241, Mongol detachments entered the Margravate of Meissen and the March of Lusatia following a decisive Mongol victory at the Battle of Legnica in Poland. The