But we are able to grasp from the extensive label text and documents that as the war unfolded, a new attitude was taking shape that was rooted in the soldiers’ experiences. It has had an enduring influence on how war itself is often thought about — with complicated consequences.

Before 1914, wars were not typically considered pointless, gratuitously violent enterprises; they could be foolish or misguided, but they were generally considered instrumental exercises of political power. Before 1914, wars were also not typically presumed to be suspect before proven necessary. Now, with few exceptions, they often are. Of course, nuclear weaponry contributed to this change. And other qualifications are needed: Some wars will inspire widespread support; some will even be broadly seen as necessary. But the premises have shifted, particularly in cultural life.

What about this particular war contributed to the shift? It wasn’t just the experience of trauma and death. In the United States, the Civil War provided plenty of both — with perhaps 750,000 dead in four years — without leading to anything comparable. Moreover, large-scale brutality is not a novelty in warfare’s history. The new attitudes seem to have arisen out of a growing sense of the war’s purposelessness, leading to broad disenchantment.

Much of this impression really did come from personal experience like the gruesome trench battles. Recent portrayals of the First World War in museums accept this view, even in such different institutions as the National World War I Museum in Kansas City, Mo., and the Museum of the Great War in Meaux, France. They are taking the lead from historians; this is history written from “below” — through the lens of ordinary participants, not political leaders or military strategists. Now, World War I tends to be thought about as if it were the product of an out-of-control mechanism for which all governments were responsible, at the cost of the human victims.