One hundred years ago, on June 28, 1914, the Archduke Franz Ferdinand of Austria-Hungary was assassinated by Serbian terrorists. The murder set off a chain reaction that plunged much of the world into war. The Great War killed 10 million people, redrew the map of Europe, and marked the rise of the United States as a global power. Here are 40 maps that explain the conflict — why it started, how the Allies won, and why the world has never been the same.