Fatalism is when two trains race toward each other on one track and no one applies emergency brakes, mistakenly assuming a full-speed collision is destined to happen. Tragedy is when either train could shift onto a siding, but neither does because neither engineer thinks he should give way.
World War I, which ended 90 years ago on Nov. 11, was a tragedy because it grew out of the German, Russian, Austrian, French, and British arrogance that took relatively minor differences in governance and elevated their defense to matters of principle. Yes, Britain could point to German autocracy, but the differences between London and Berlin (both, after all, pledging allegiance to the same royal family) weren't all that great.
And what were the Russian and Austro-Hungarian empires fighting about? Barbara Tuchman's The Guns of August (1962; new edition by Presidio, 2004) is a wonderfully readable history of the awful summer month that 94 years ago led to horror. John Keegan's The First World War (Knopf, 1999) is a fine overview of how the war dragged on until the United States under President Woodrow Wilson tipped the balance in favor of England and France-with consequences that led to an even more terrible war two decades later.
World War II and what some have called World War III (the cold war that ended in U.S. victory in 1991) were wars of principle that had to be fought, but if I had been around and thinking Christianly from 1914 through 1918, I suspect I would have been a pacifist. Many in the trenches certainly wanted to be: Silent Night: The Story of the World War I Christmas Truce (Free Press, 2001) is the amazing story of soldiers on both sides in December 1914 laying down their arms temporarily. They sang carols, exchanged gifts, and even played soccer together during the unofficial (and officially frowned-on) truce.