sent spies into Poland and Hungary, and as far as eastern Austria, in preparation for an attack into the heartland of Europe. Having a clear picture of the European kingdoms, he prepared an attack nominally commanded by Batu Khan and two other familial-related princes. Batu Khan, son of Jochi, was the overall leader, but Subutai was the strategist and commander in the field, and as such, was present in both the northern and southern campaigns against Rus' principalities. He also commanded the central column that moved against Hungary. While Kadan's northern force won the Battle of Liegnitz and Güyük's army triumphed in Transylvania, Subutai was waiting for them on the Hungarian plain. The newly reunited army then withdrew to the Sajó river where they inflicted a decisive defeat on King Béla IV of Hungary at the Battle of Mohi. Again, Subutai masterminded the operation, and it would prove one of his greatest victories. Invasion of Poland The Mongols invaded Central Europe with three armies. One army defeated an alliance which included forces from fragmented Poland and their allies, led by Henry II the Pious, Duke of Silesia in the Battle of Liegnitz. A second army crossed the Carpathian mountains and a third followed the Danube. The armies re-grouped and crushed Hungary in 1241, defeating the Hungarian army at the Battle of Mohi on April 11, 1241. The devastating Mongol invasion killed half of Hungary's population. The armies swept the plains of Hungary over the summer, and in early 1242 regained impetus and extended their control into Dalmatia and Moravia. The Great Khan had, however, died in December 1241, and on hearing the news, all the "Princes of the Blood," against Subotai's recommendation, went back to Mongolia to elect the new Khan. After sacking Kiev, Batu Khan sent a smaller group of troops to Poland, destroying Lublin and defeating an inferior Polish army. Other elements—not part of the main Mongol force—saw difficulty near the Polish-Halych border. The Mongols then reached Polaniec on the Czarna Hańcza, where they set up camp. There, the Voivode attacked them with the remaining Cracovian knights, which were few in number, but determined to vanquish the invader or die. Surprise gave the Poles an initial advantage and they managed to kill many Mongol soldiers. When the invaders realized the actual numerical weakness of the Poles, they regrouped, broke through the Polish ranks and defeated them. During the