Using the power of the Google, here's what I found..in fractions of a second no less. I know there are subtleties that may escape you, but a little effort and critical thinking may enlighten you.
June 28 Assassination of Archduke Franz Ferdinand of Austria, heir to the Austro-Hungarian throne, who was killed in Sarajevo along with his wife Duchess Sophie by Bosnian Serb Gavrilo Princip.
July 5 Austria-Hungary seeks German support for a war against Serbia in case of Russian militarism. Germany gives assurances of support
July 23 Austria-Hungary sends an ultimatum to Serbia. The Serbian response is seen as unsatisfactory
July 28 Austria-Hungary declares war on Serbia. Russia mobilizes.
July 31 Germany warns Russia to stop mobilizing. Russia says mobilization is against Austria-Hungary only.
August 1 Germany declares war on Russia, France and Belgium begin full mobilization.
And so on and so on....
Germany was an enthusiastic participant in the War, but without the preface, they would not have invaded Belgium and Luxembourg.....perhaps in a pre-emptive move against France, because they felt it was coming anyway?