Jacques-Louis David painted The Death of Marat in approximately three months between July and November 1793, immediately after the assassination of Jean-Paul Marat in his Paris bath on 13 July 1793. The 165 × 128 centimetre oil-on-canvas hangs Marat dead in the green-curtained wooden tub he used to soothe his chronic skin disease, the murder weapon — Charlotte Corday's small kitchen knife — visible on the floor.

Guernica is the most famous anti-war painting of the twentieth century — but it is also a specific argument, built piece by piece out of a visual grammar Goya invented in 1814. The bull, the horse, the lit lamp, the screaming mother, the broken sword. What each part of Guernica says, and the line of paintings that taught Picasso how to say it.

Before Goya, European painters showed war as triumph. After Goya, they could no longer pretend. The Third of May 1808 ended the heroic battle picture and invented the painting of senseless violence — a tradition that runs through Manet, Picasso, and every photograph of war we have made since.

A man in a white shirt throws his arms wide before a firing squad on a hill above Madrid. Goya painted the night six years after it happened — and built every modern war painting that came after.