Austria-Hungary's ultimatum to Serbia, issued on July 23, 1914, consisted of ten demands that were designed to undermine Serbian sovereignty. Key terms included the suppression of anti-Austrian Propaganda, the dismissal of officials implicated in anti-Austrian activities, and the acceptance of Austro-Hungarian officials to participate in the investigation of the assassination of Archduke Franz Ferdinand. Serbia accepted most of the demands but rejected some, particularly those infringing on its sovereignty, leading Austria-Hungary to declare war on Serbia on July 28, 1914.
Austria sent the ultimatum to Serbia on July 23rd 1914
Serbia
Serbia partially accepted the ultimatum from Austria-Hungary but rejected some of the demands. This led to Austria-Hungary declaring war on Serbia, which ultimately sparked the beginning of World War I.
23rd July 1914
Austria issued Serbia a 10-part ultimatum in response to the role of Serbian and Slavic nationalists in the assassination of the Austrian archduke.
Because the the Archduke Franze Ferdinand was the heir to the Austria-Hungary throne when him and his wife when assassinated by a Serbian Nationalist in Sarejevo. Austria Hungry Gave Serbia a ultimatum and when Serbia did not follow the ultimatum Austria-Hungry declared war with Serbia
When Serbia responded to Austria-Hungary's ultimatum, they accepted all the conditions save one. Austria-Hungary immediately declared war on Serbia, which had always been their intention given the demeaning demands they had made.
Germany could have refused to back Austria on the grounds that the ultimatum to Serbia was too harsh. ;)
I am guessing that this question is referring to the Ultimatum given by the Austria-Hungarian government to Serbia just before WW1. The whole point of the conflict between Serbia and Austria at the time was a conflict between Russia and Austra fighting for allegiance of the strongest country in the Balkans, and Serbia feeling threatend in its sovereignty. The ultimatum was in a form which was apparent to everyone that Serbia could not accept, since the political consequences of agreeing to it and loosing a war were the same.
when Serbia refused to comply with Austria- Hungary's ultimatum
Austria was rightly angered. They issued an ultimatum to Serbia to right the wrongs committed, but the ultimatum was too much for just an assassination. Serbia didn't reply and Russia stepped in to help the small Slavic brother. That move turned the two-nation conflict into a war.
The assassination of Archduke Franz Ferdinand of Austria, by Gavrilo Princip on June 28, 1914. On July 23, 1914, Austria set an ultimatum for Serbia to leave Austria. This ultimatum would expire on July 28, 1914. When the Serbs would still not leave, Austria declared war on Serbia.