The Battle on the Marchfeld (i.e. Morava Field; Czech: Bitva na Moravském poli) at Dürnkrut and Jedenspeigen took place on 26 August 1278 and was a decisive event for the history of Central Europe for the following centuries. The opponents were a Bohemian (Czech) army led by the Přemyslid king Ottokar II of Bohemia and the Imperial army under the German king Rudolph I of Habsburg in alliance with King Ladislaus IV of Hungary. Although both sides had in their units also infantry, the battle itself was primarily a great collision of heavy knights cavalry, though the Cuman horse archers in the Hungarian army played a vital role. The battle was finally won by an ambush attack of the united Imperial-Hungarian forces, which was in those times considered dishonourable and against the rules of kni