Next year marks the 70th anniversary of the destruction of Guernica. It's about time Madrid heeded the Basque demands for that painting. (Colm Tóibín Saturday April 29, 2006)

Picasso was in Paris when Guernica was bombed. The devastating air attack on the Basque town on April 26 1937 was widely reported. The following day, George Lowther Steer wrote in the Times: "Guernica, the most ancient town of the Basques and the centre of their cultural tradition, was completely destroyed yesterday by insurgent air raiders. The bombardment of the open town far behind the lines occupied precisely three hours and a quarter during which a powerful fleet of aeroplanes ... did not cease unloading on the town bombs weighing from 1,000lbs downward and it is calculated more than 3,000 two-pounder aluminium incendiary projectiles. The fighters, meanwhile, plunged low from above the centre of the town to machine-gun those of the civilian population who had taken refuge in the fields."

The following morning the headlines in L'Humanité, the morning newspaper Picasso usually bought, read: "MILLE BOMBES INCENDAIRES lancées par les avions de Hitler and Mussolini". It was accompanied by graphic pictures of the devastated town and photographs of the casualties.

For the Basques, it was an attack on the soul of their ancient nation; for the world, it was a crime against humanity. As time went by, as the name Guernica became associated with a picture rather than a place, many Basques took a dim view of a painting made far away by someone who had no special affinity with Basque culture. In recent years, however, as that culture has become more open, people in the Basque country have wondered why Picasso's painting should hang only in Madrid, why it has never crossed their borders to hang in the place where the crime was committed. They, and many others in Spain, want to see this great icon on show in Bilbao or in Guernica itself.

By the time of the bombing, Picasso had, along with other artists such as Joan Miró and Julio González, been commissioned by the Spanish republican government to design a work for the international exhibition in Paris at the Spanish pavilion in 1937. He had visited the site of the pavilion, designed by Josep Lluís Sert and Luis Lacasa. He had seen the large space his mural was to fill.

By this time he had also made two of the series of six grotesque etchings called Dream and Lie of Franco. Yet there were still rumours that he supported the fascists, or had remained indifferent to what was happening in Spain, enough for him to issue a statement as he worked on Guernica: "The Spanish struggle is the fight of reaction against the people, against freedom. My whole life as an artist has been nothing more than a continuous struggle against reaction and the death of art. How could anybody think for a moment that I could be in agreement with reaction and death? ... In the panel on which I am working, which I shall call Guernica, and in all my recent works of art, I clearly express my abhorrence of the military caste which has sunk Spain in an ocean of pain and death."

Picasso had by that time found a large studio in Paris, with rich associations, where he could work on his mural. It was in rue des Grands-Augustins, about which Balzac had written, and in a building that had more recently been used by the surrealist George Bataille for meetings that Dora Maar had attended. The building had an enormous attic. Picasso had no excuse not to work, but in the weeks before he read about the air raids on Guernica there is no evidence that, despite some efforts, he had any great ideas about the commission.

The reports of the bombing, which had killed 1,645 people and injured 889, made it clear that it had been an indiscriminate attack on a civilian population. The Times reported: "In the form of its execution and the scale of the destruction it wrought, no less than the selection of its objective, the raid on Guernica is unparalleled in military history." Picasso, as well as feeling outrage, had the fate of his family and friends in Barcelona to worry about.

On May 1 he made his first sketch. The process of making the mural was recorded by Maar. Two years earlier Picasso had mused: "It would be most interesting to preserve photographically not the stages but the metamorphoses of a painting ... But there is one very odd thing - to notice that basically a picture does not change, that the first vision remains almost intact, despite appearances." This first sketch on a piece of blue paper had the bull, the bird, the dead horse with the raised hind legs and the woman.

Gijs van Hensbergen, in his definitive book Guernica: The Biography of a 20th Century Icon, writes about that first day's work: "There is nothing in the first preparatory sketch for Guernica that specifically describes Gernika [the Basque spelling], the bombing, the planes, the effect of incendiaries, the fingers of flame, or the crashing explosions and the array of corpses. From sketch 2 through sketch 6, all produced on that first day, Picasso ... repositions his actors and discards those extraneous to the plot, slowly refining and paring them back ... By the evening of May 1, he had come remarkably close to the finished painting."

Each weekday that May Picasso worked on the painting, allowing Maar to photograph the process, and at weekends he went to the country to be with Marie Thérèse Walter. At the end of the month he invited friends and artists, including Alberto Giacometti, Roland Penrose and Henry Moore, to see the work in progress. Moore remembered: "You know the woman who comes running out of the little cabin on the right with one hand held in front of her? Well, Picasso told us there was something missing there, and he went and fetched a roll of paper and stuck it in the woman's hand, as much as to say that she'd been caught in the bathroom when the bombs came."

On July 11, the day before the opening of the pavilion, the writer Max Aub spoke to those who had worked on its construction: "At the entrance, on the right, Picasso's great painting leaps into view. It will be spoken of for a long time. Picasso has represented the tragedy of Gernika. It is possible that this art will be accused of being too abstract or difficult for a pavilion like ours which seeks to be above all, and before everything else, popular manifestation ... To those who protest saying that things are not thus, one must answer asking if they do not have two eyes to see the terrible reality of Spain. If the picture by Picasso has any defect it is that it is too real, too terribly true, atrociously true."

So began the arguments about the painting. Was it a poster or a painting? Did it represent the horror of war or some rather personal obsessions of the painter coupled with some art history? What did the bull signify? Was it a new beginning for public art, for pictorial space, for the depiction of horror? The mural was placed in the most central part of the pavilion. The controversy over its value began immediately, with the president of the Basque country less than enthusiastic about the work, declining Picasso's offer of the painting "for the Basque people". The Basque muralist José María Ucelay also took a dim view of it. "As a work of art," he said, "it is one of the poorest things ever produced in the world ... It is just seven by three metres of pornography, shitting on Gernika, on Euskadi [the Basque country], on everything." These remarks rest among the many made in these years by Spaniards of all sorts which need, in the light of current opinion, to be swiftly forgotten.

After its exhibition in Paris, the painting moved to London, arriving on September 30 1938, the day of the Munich pact. In January 1939, both painting and preparatory sketches were shown at the Whitechapel Art Gallery, where 15,000 people came to see it in the first week. Then it was moved to the US, where it was shown at the Museum of Modern Art in New York and subsequently around the country and later in the 1950s in Brazil and various European venues. But the touring did not help its fragile state. Picasso decided that it should stay in New York where "it slowly moved", Van Hensbergen writes, "from the condition of witness and prophecy back into the safer realms of artefact".

However, because Picasso had also stated that the painting could be moved to Spain once fascism ended there, it became a symbol of hope that, after Franco's death, Spain would become a republic. The arrival of Guernica in Spain would mean that the nightmare which Franco had created was over. As the regime softened, a Picasso museum opened in Barcelona and there were suggestions that the painting could return, but Picasso was adamant, as was his family after his death. The painting would come only with democracy.

Thus it did not arrive on Spanish soil until September 10 1981, almost six years after Franco's death. It was placed on exhibition behind bomb and bullet-proof glass. Then, after much further controversy, in 1992 the painting and the sketches were moved to the new Museo Reina Sofía in Madrid. Requests to have Guernica exhibited in Guernica itself, or in Barcelona during the Olympic games, were refused because of its fragile state.

In 1992 the Basques did not have a space for the painting at the new Guggenheim Museum in Bilbao. But, just as Guernica became a symbol for resistance to Franco, this astonishing building, designed by Frank Gehry and opened in 1997, has become a symbol for a new Basque confidence, both cultural and political. The Basque cultural legacy is complex. On one hand, it is a deeply nationalist culture that has preserved an ancient language and sense of identity; on the other, because of its prosperity, its openness to France and to the sea, it has long been a most cosmopolitan society. It is no mistake that the playful new museum made to house the best of international art was designed by an outsider, or that the wonderful new bridge in Bilbao was designed by Santiago Calatrava, also an outsider.

Late last year I travelled through the country for BBC Radio 3 to look at the Basque musical heritage. As a mountainous region, it is of course rich in folk song and, as a society that has been deeply Catholic, its religious and choral heritage is strong. But many Basque classical composers, including Juan Crisóstomo Arriaga, called the Spanish Mozart, have steeped themselves in French and German influences. It is possible to listen to the music of many Basque composers, both contemporary and classical, and feel that the influence of the outside world has been paramount. Of all the features of the Basque country, this tradition is the most hidden and, in some ways, the most typical.

It has been hard perhaps to publicise such cultural treasures as Arriaga, Pablo Sarasate, Jesús Guridi, Jesús Arámbarri, Luís de Pablo or indeed Maurice Ravel in the musical world while the Eta campaign held the headlines. Since Eta has declared a ceasefire, the changes in the society, apparent for a long time to those who live there, may become clear to the outside world. As in Ireland, the vacuum left by political violence can most usefully be filled by culture.

The Basque demand for Picasso's Guernica to be put on display in their showcase building, or in some other suitable venue, is thus clever and interesting. In recent years the Catalans have run a superbly orchestrated campaign for the return of archives that were taken from Catalonia to Salamanca at the end of the civil war by Franco's troops. It was the Madrid government's opposition that gave the campaign much oxygen. Earlier this year the return of the archives to Barcelona was a cause of pride and joy for Catalan nationalists.

So, too, in the Basque country the main nationalist party and the main conservative party have joined forces with other Spanish politicians in calling for Guernica, so disliked by certain Basques in 1937, to be taken from Madrid. It would be very foolish of those who control the painting, no matter how fragile its state, to allow it to become a symbol of Spanish centralism. The campaign to hand it over, for however brief a time, is likely to become a great Basque rallying cause the longer it goes on.
· Colm Tóibín's novel The Master (Picador), was shortlisted for the Booker prize in 2004. His radio series, God, History, Fantasy and Reason - A Journey through Spanish History and Music, begins tomorrow at 3.30pm on Radio 3

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