Battle on the Marchfeld

The Battle on the Marchfeld 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 army led by the Přemyslid king Ottokar II of Bohemia and the German army under the German king Rudolph I of Habsburg in alliance with King Ladislaus IV of Hungary. With 15,300 mounted troops, it was one of the largest cavalry battles in Central Europe during the Middle Ages. The Hungarian cavalry played a significant role in the outcome of the battle.

King Ottokar II of Bohemia expanded his territories considerably from 1250 to 1273, but suffered a devastating defeat in November 1276, when the newly elected German king Rudolph I of Habsburg imposed the Imperial ban on Ottokar, declaring him an outlaw and took over Ottokar's holdings in Austria, Carinthia, Carniola, and Styria.

Source: Wikipedia