In 1970, at the height of the opposition to the Vietnam War, a group of American artists including Louise Bourgeois (whose works are on display in Sydney right now) and Donald Judd signed an open letter demanding that the artist Pablo Picasso remove one of his greatest lifeworks, the painting Guernica, from the Museum of Modern Art in New York. When war broke out in Europe in 1939, Picasso asked the art institution to take in and safeguard the monumental painting of the 1937 Nazi bombing of the Basque town. But by the late '60s, that painting of broken bodies...