Austria-Hungary issued an ultimatum to Serbia after Franz Ferdinand, the archduke of Austria, was assassinated along with his wife in Serbia. On July 23, 1914 (about a month after the assassination), the government of Austria-Hungary issued an ultimatum to Serbia. The ultimatum demanded that Serbia would ...
allow Austria-Hungary to conduct an investigation into the assassination;
stop all anti-Austrian propaganda being circulated in Serbia;
eliminate all terrorist groups such as the Black Hand, which was the group believed to be responsible for the archduke's assassination.
The government of Austria-Hungary demanded an answer from Serbia's government within 48 hours, or war would happen. And war did happen -- a conflict that ended up involving many other countries, which we now call World War I.
Here is a brief summary of this answer. At six o'clock in the evening on July 23, 1914, nearly one month after the assassination of Austrian Archduke Franz Ferdinand and his wife by a young Serbian nationalist in Sarajevo, Bosnia, Baron Giesl von Gieslingen, ambassador of the Austro-Hungarian Empire to Serbia, delivers an ultimatum to the Serbian foreign ...
