Hi Spencer. Thank you for sending your question. Here is what I found -
The simplest answer is that the immediate cause was the assassination of Franz Ferdinand, the archduke of Austria-Hungary. His death at the hands of Gavrilo Princip – a Serbian nationalist with ties to the secretive military group known as the Black Hand – propelled the major European military powers towards war.May 31, 2016
I also looked at Canada's involvement in World War I on the Virtual Learning Commons in Canada in Context. Below is the database you should look at. Enter World War I in the search box.
http://ic.galegroup.com/ic/cic/?userGroupName=ko_k12elm_d65
