The Decline of the Ottoman Empire allowed Austria-Hungary to spread it's influence in Bosnia which upset the ballance between the Great Powers in that Region (Austria Hungary, Russia, & The Ottoman Empire) If the Ottoman Empire was stronger Bosnia would have stayed firmly under Ottoman control. Which would have prevented a rift between Austria-Hungary & Bosnian-Serbs. Making an Assassination attempt on the Heir to the Austro-Hungarian throne, Archduke Franz Ferdinand of Austria in Sarajevo, Bosnia In 1914 extremely unlikely