World War I yielded a number of striking and affecting pictures. Some, included in the gallery of 380 presented in The Great War: A Photographic Narrative, are famous: the line of gassed men, blinded and clutching each other’s shoulders as they approach a first-aid station in 1918; the haunting, charred landscapes of the Ypres Salient in 1917. And yet in both cases, the more-renowned versions were their painted successors of 1919: John Singer Sargent’s oil painting Gassed, and Paul Nash’s semi-abstract rendering of the blasted Belgian flatland, The Menin Road. The essence of the Great War lies in the absence of any emblematic photograph.