How the Croats actually saved central Europe from the Mongols

At Klis Fortress the Mongols experienced defeat in 1242.

 During the Middle Ages, the Kingdom of Croatia was in a personal union with the Kingdom of Hungary, with Béla IV as a king.When routed on the banks of the Sajo 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) suffered a major defeat at Klis Fortress in Croatia in March 1242. 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 their defeat against 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 set up in mountain passes.Most historians claim that the death of Ögedei Khan was the primary reason for retreat. In any case, though much of Croatia was plundered and destroyed, long-term occupation was unsuccessful.