Excerpts from Books and Wikipedia
"In spring 1241, the Mongols, who had already conquered a vast area of Eurasia from China to the Ukraine, pushed into Hungary and Poland. . . . Well informed of the movements of the Christian forces, the Mongols in Poland moved to attack Henry before he could join with Wenceslaus. . . . Almost the entire Christian force, perhaps 20,000 men, was massacred. . . . The Hungarian army was soon also defeated, leaving western Europe wide open to Mongol invasion. This was prevented by the fortuitous death of the Mongol leader, the Great Khan Ogatai. The Mongols had to journey back to their distant capital, Karakorum, to choose his successor, and were never to mount a full-scale invasion of Europe again." [Furtado: 1001 Days]