On June 28, 1914, in the dusty Balkan town of Sarajevo, an assassin fired two shots. In the next five minutes, as the stout middle-aged Archduke Franz Ferdinand of Habsburg, heir to the Austro-Hungarian throne, and his wife bled to death, a dynasty-and with it, a whole way of life-began to topple. In the ages before World War I, four dynasties-the Habsburg, Hohenzollern, Ottoman, and Romanov-dominated much of civilization. Outwardly different, they...