On a day like today...
1456
The siege of Belgrade had fallen into stalemate when a spontaneous fight broke out between a rabble of Crusaders, led by the Benedictine monk John of Capistrano, and the city's Ottoman besiegers. The melee soon escalated into a major battle, during which the Hungarian commander, Janos Hunyadi, led a sudden assault that overran the Turkish camp, ultimately compelling the wounded Sultan Mehmet II to lift the siege and retreat.
1914
Austria and Hungary issued an ultimatum to Serbia after the assassination of Archduke Ferdinand; the dispute led to World War I.