The Battle of Mohi (11 April 1241), also known as Battle of the Sajó River or Battle of the Tisza River, was the main battle between the Mongol Empire and the Kingdom of Hungary during the Mongol invasion of Europe. It took place at Muhi (then Mohi), southwest of the Sajó River. The battle resulted in a victory for the Mongols, who destroyed the Hungarian Royal army. Background The Mongol invasion of Europe The Mongols attacked the eastern side of Central Europe with five distinct armies. Two of them attacked through Poland in order to protect the flank from Polish cousins of Béla IV of Hungary, winning several victories. Most notably, they defeated the army of Duke Henry II the Pious of Silesia at Legnica. A southern army attacked Transylvania, defeated the voivod and crushed the Transylvanian armies. The main army led by Khan Batu and Subutai attacked Hungary through the fortified Verecke Pass and annihilated the army led by Denis Tomaj, the count palatine, on 12 March 1241, while the final army under Batu's brother Shiban marched in an arc north of the main force. Prior to the invasion, King Béla had personally supervised the construction of dense natural barriers along Hungary's eastern border, intending to slow the Mongol advance and obstruct their movement. However, the Mongols possessed specialized units who cleared the paths with great rapidity, removing the obstacles in just three days. Combined with the extreme speed of the Mongol advance, called "lightning" by a European observer, the Hungarians lacked time to properly group their forces. Warnings and Hungarian preparations In 1223, the expanding Mongol Empire defeated a group of semi-allied Rus city states at the Kalka River using their famous tactic of the feigned retreat under Subutai and Jebe. This was part of their great cavalry raid to explore the lands beyond their knowledge under the direction of Genghis Khan. The defeated princes of Rus who were captured by the Mongols were crushed to death under a victory platform following the battle. At this time, the Mongols were purely an expeditionary force in Europe, and did not besiege major cities such as Kyiv until decades later, under the direction of Genghis Khan's son and successor, Ogedei. Hungary had tried to convert the Cumans to Christianity and expand its influence over them for several decades beforehand. The Hungarian king Béla IV even began to use the title