If you listen closely, you can hear the guns of August blasting a decade and more before WWI actually began.
Fromkin (History/Boston Univ.; The Way of the World, 1999, etc.) delivers a thesis that will be new to general readers (though not to specialists): WWI came about because of the very different, but conveniently intersecting, ambitions of the German and Austro-Hungarian empires, and the signs were evident long before the fighting began. The Habsburgs wanted to crush Serbia, which they (perhaps rightly) perceived to be a potent threat to Austro-Hungarian designs in the Balkans; the Austrian chief of staff “first proposed preventive war against Serbia in 1906, and he did so in 1908–9, in 1912–13, in October 1913, and May 1914: between 1 January 1913 and 1 January 1914 he proposed a Serbian war twenty-five times.” Just so, the Kaiser wanted to crush Russia, which he regarded as Germany’s one real rival for European dominance; war against Serbia would provide a useful pretext, though it wasn’t essential. Indeed, writes Fromkin, when a Slavic nationalist assassinated Archduke Franz Ferdinand on June 28, 1914, in Sarajevo, the rest of Europe practically yawned; even Austria did not retaliate immediately, despite Germany’s urging to get on with the game. “Austria did not play its part very well,” Fromkin writes, and did not even bother declaring war on Germany’s enemies until some time after the war had actually begun. Similarly, Germany neglected to declare war on Serbia, “the only country with which Austria was at war and which, according to Vienna, was the country that posed the threat to Austria’s existence.” Fromkin’s notion that a pan-German conspiracy caused WWI is credible, even if the events he describes sometimes seem more a comedy of errors than a model of efficient militarism.
Still, his account of the war's origins, though surely arguable at many points, fills in many gaps.