This article by David Cohen in Slate (via James Russell) discusses the history of Picasso's Guernica , including its use as a symbol by various anti-war groups, and the continuing bickering over its location. As mentioned in the article, the painting was moved from the Museum of Modern Art in New York to the Prado (and eventually the Reina Sofia) in Madrid, as Picasso had specified that the painting should be given to Spain once Franco was dead and Spain was a democracy. However, Cohen does not discuss the further chapter of bickering that has followed this. He writes:

In the first Spanish monograph on Picasso, published in Madrid in 1951, the author described Guernica as "the picture of all bombed cities"—a neat formulation that underscores the cost of universalism in art. Lack of specificity makes the image more potent and more tame.

Of course, there is one group of people who don't see Guernica as a picture of all bombed cities, or if they do this is secondary. These are the actual people of Guernica, and Basque people in general. The town of Guernica was the Basque's ancient capital, and their national assembly met once a year under the great oak tree of Guernica. (When Guernica was bombed, the town was almost completely destroyed, but the oak tree survived).

Unsurprising, the Basques to this day take the bombing of Guernica very personally, and the painting is considered by them to be a part of their heritage. (In the Basque country of northern Spain, you see images of the painting everywhere). The Basque terrorist group ETA exists because of the brutality of the Franco regime towards the Basques, and (although ETA was founded decades later) the bombing of Guernica was perhaps the most extreme example of this brutality.

For this reason, the Basques think that the painting should not be in Madrid but in the Basque country. And as it happens, a major new museum of modern art, the new Guggenheim museum, was built recently in Bilbao, modern capital of the Basque country, and just down the road from Guernica. The Basques strongly believe that the painting belongs there, and have been agitating for it to be given to them. It is extremely unlikely that this will happen any time soon, particularly given that relations between Basque separatists and Madrid are at an extremely low point at the moment. The Guggenheim Bilbao requested a loan of Guernica to commemorate the opening of the museum in 1997. However, the authorities in Madrid refused, believing (quite possibly accurately) that if the painting every went to Bilbao it would never come back again. Look for the saga to continue.