A war fought between two alliance systems across Europe, the Middle East, Africa, and the oceans — the first industrial-scale conflict in history, which killed roughly 20 million people, destroyed four empires, redrew the political map of the world, and created the conditions for the Second World War.
The First World War was not an accident caused by one assassination. It was the product of a European political system that had been arming itself, allying itself, and rehearsing its anxieties for forty years — a system so tightly wound that when the trigger was finally pulled in Sarajevo, it discharged everything at once. The war that followed consumed a generation, destroyed four empires, and produced a peace settlement so punishing that it made the next war almost inevitable. Understanding the First World War is a precondition for understanding the twentieth century.