Not long after the outbreak of the First World War, Gertrude Stein and Pablo Picasso were walking along the Boulevard Raspail in Paris when they saw a camouflaged truck. ‘It was at night,’ Stein recalled with uncharacteristic clarity, ‘we had heard of camouflage but we had not yet seen it and Picasso amazed looked at it and then cried out, yes it is we who made it, that is cubism.’

Picasso must have been looking at one of the early works by France’s newly formed Section du Camouflage. In peacetime its commander, Lucien-Victoria Guirand de Scévola, had been a Symbolist working in pastels, but in war he modernised for the nation. ‘In order to deform totally the aspect of an object,’ he wrote, ‘I had to employ the means that Cubists used to represent it.’

The word camouflage is a First World War coinage, derived from Parisian slang: the literal meaning of camoufler is ‘to blow smoke in someone’s face’. Yet the mobilisation of art for warfare was a 19th-century innovation, inseparable from contemporary science. Darwin had examined the value of ‘protective coloration’ for survival.