World War I began when The Arch Duke of Austria-Hungary and his wife were assassinated by I believe a Serb on August 28, 1914.
What if that assassination had never happened?
I know, the short answer is, no WWI. But the tensions that led to that assassination and to WWI would still have been there and would at some point have been released.
If it had not begun in 1914, when would WWI have begun and how would a later WWI have effected history?