Causes of World War I

On June 28, 1914, a tubercular Bosnian Serb teenager named Gavrilo Princip shot the heir to the Austro-Hungarian throne, Archduke Franz Ferdinand, in Sarajevo. Within six weeks, every major European power but Italy was at war. No one had wanted that war — at least, no one had wanted this war. Many soldiers and civilians hoped for a short war, while general staffs pursued rapid victories before enemy coalitions could bring their full resources to bear. Others warned that industrial powers could sustain a long struggle. No government had a reliable timetable for what followed. Then came four years of industrial slaughter that killed about ten million soldiers, maimed twenty million more, toppled the Romanov, Habsburg, Hohenzollern, and Ottoman dynasties, and seeded the revolutions, depressions, and ideologies that would consume the rest of the century.

The war's causes are still argued about — German Griff nach der Weltmacht, blundering diplomacy, the iron logic of mobilization — but the consensus shape is something like a continent overloaded with dynamite and short on circuit-breakers. Two rigid alliance systems (the Triple Entente of France, Russia, Britain; the Triple Alliance of Germany, Austria-Hungary, Italy) meant any bilateral quarrel in the Balkans could escalate to continental war — and the Balkans were already smoldering after the annexation of Bosnia in 1908 and two regional wars in 1912–13. Mobilization timetables — drafted by general staffs in peacetime, above all Germany's Schlieffen Plan — were so dependent on railway schedules that, once started, they could not be halted without losing the war you had not yet begun; Russian general mobilization on 30 July forced the German hand, and the German plan ran through Belgium, whose violated neutrality brought in Britain on 4 August. A century of romantic nationalism had taught populations to want a heroic conflict, and an Anglo-German naval arms race over Dreadnought battleships had hardened mutual suspicion into certainty. So the diplomats of the July Crisis, faced with a quarrel they thought they could localize, each took one defensive step after another — the Austrian ultimatum, the German blank cheque to Vienna, the Russian mobilization — until none of them controlled the outcome. The war is the canonical example of a structural trap: locally rational decisions producing collective catastrophe that every actor would have paid almost anything to avoid, and it discredited the very statecraft — secret treaties, balance-of-power maneuvering — that had kept the peace for forty years.