To walk the orderly rows of headstones in the elegant graveyards that hold the dead of World War I is to feel both awe and distance. With the death of the last veterans, World War I, which began 100 years ago, has moved from memory to history. But its resonance has not faded — on land and geography, people and nations, and on the causes and consequences of modern war.

The memorial here at Tyne Cot, near Ypres and the muddy killing ground of Passchendaele, is the largest British Commonwealth cemetery in the world. Nearly 12,000 soldiers are buried here — some 8,400 of them identified only as “A Soldier of the Great War, Known Unto God.” Despite the immensity of this space, the soldiers represent only a tiny portion of the 8.5 million or more from both sides who died, and that number a fraction of the 20 million who were severely wounded.

In Europe’s first total war, called the Great War until the second one came along, seven million civilians also died.