Today marks the 100 year anniversary of the assassination of Archduke Franz Ferdinand, furthering the uneasy conditions which set in motion World War I. No greater marker exists to divide the world from the Ancien Regime and the modern world of mechanized warfare.
For the most thorough and fascinating description of WWI, see historian Barbara Tuchman’s Guns of August, and/or preceding that, The Proud Tower. You won’t be disappointed.
(^read it and weep.)