When you think of all the horrors of the 20th century, such as  the Holocaust, the Bolshevik Revolution and World War II, were it not for the assassination of Austro-Hungarian Archduke Franz Ferdinand, none of these would have ever happened. Appearing on PragerU, historian and author Andrew Roberts explains the unfortunate series of events that led to World War I and the deaths of 16 million soldiers and civilians, and changed the world forever.