In the 1940s, while he was in Nazi-occupied France, Pablo Picasso was once visited in his studio by a German officer. Seeing a photograph of Picasso standing before Guernica, his 1937 painting of the Nazi bombing of the eponymous town in Basque country in northern Spain during the Spanish civil war, the officer asked him: “Did you do that?” “No you did it,” was the artist’s response. Guernica is largely considered one of the most powerful anti-war artworks of the 20th century. It is also a slice of Spain’s eventful, bloodied history, which saw cultural wars, colonial conquests and fascist...