When I reviewed the first volume of Sir Ian Kershaw’s wrist-breaking history of the last 100 years of Europe, To Hell and Back, in these pages exactly three years ago, I compared our continent in 1945 to a punch-drunk boxer rising from the canvas with both eyes blacked. How, I wondered, would Kershaw handle the battered old bruiser coping with a not-so-brave new world in which he was no longer the undisputed champ?

The image of the wounded fighter, I think, was apt, for the red thread running through Europe in the first half of the century, as Kershaw rightly saw,...