William Hogarth, O the Roast Beef of Old England (The Gate of Calais), 1748, oil on canvas Tate Britain, London

Spring is here in Paris, and so is the army. Camouflaged soldiers with assault rifles patrol the airports and train stations, and armed police loiter on street corners. Since last November’s Islamist massacres, the police have conducted more than 2,500 raids and held hundreds of suspects. In mid-February, the National Assembly voted to extend the state of emergency by another three months. The Assembly also endorsed the first part of the Hollande...