WWI was one of the most costly and the most gruesome of wars that mankind has ever seen. It was also one of the most pointless. I've just finished reading The First Casualty, a ripper of a novel by author and playwright Ben Elton. The novel is set in 1917, and much of the story takes place at the infamous Battle of Passchendaele, which is considered to have been the worst of all the many hellish battles in the war. I would like to quote one particular passage from the book, which I believe is the best summary of the causes of WWI that I've ever read.
Soccer (or football) is the most popular sport in the world today; likewise, with over 700 million viewers, the 4-yearly FIFA World Cup is the most watched event in human history. Why is this so? Is it mere chance — a matter of circumstance — that soccer has so clearly and definitively wooed more devotees than any other sport? I think not. Team sports are an approximation of military battle. All such sports endeavour to foster the same strategies that can be used effectively in traditional warfare. Soccer, in my opinion, fosters those strategies better than any other sport; this is because, in tactical terms, it is the most pure sport in the modern world.