Following the assassination of Archduke Franz Ferdinand, Austria-Hungarian authorities managed to obtain information from three conspirators which seemed to implicate members of the Serbian military in the assassination. Both Austria-Hungary and Germany requested that Serbia open a judicial inquiry into the matter . . . these requests were refused.
On July 5, one week since the assassination, letters were delivered to Kaiser Wilhelm II of Germany, requesting assurance of his support if Austria-Hungary sought military satisfaction from Serbia. He gave his assurance almost immediately, and Austria-Hungary began preparations for its ultimatum to Serbia.