Much has been written about what exactly caused World War I. As befits a true global war, the reality is that there isn't a single cause. There aren't even three causes. There are a vast array of causes. Today we'll get into just a few of those causes, including the complex system of alliances in Europe, the myriad military conflicts that played out in the years and decades leading up to the war, and the event that many point to as the beginning: the assassination of Archduke Franz Ferdinand.