The First World War inaugurated the manufacture of mass deaths that the Second brought to a pitiless consummation. - John Keegan

War’s rancours are quick to bite and slow to heal.

But then the First World War is a mystery. Its origins are mysterious. So is its course. Why did a prosperous continent, at the height of its success as a source and agent of global wealth and power and at one of the peaks of its intellectual and cultural achievement, choose to risk all it had won for itself and all it offered to the world in the lottery of a vicious and local internecine conflict? Why, when the hope of bringing the conflict to a quick and decisive conclusion was everywhere dashed to the ground within months of its outbreak, did the combatants decide nevertheless to persist in their military effort, to mobilise for total war and eventually to commit the totality of their young manhood to mutual and existentially pointless slaughter?

It was broadly true that all European royalty were cousins; even the Habsburgs of Austria, most imperious of sovereigns, occasionally mingled their blood with outsiders; and since every state in Europe, except France and Switzerland, was a monarchy, that made for a very dense network of interstate connections indeed.