Picasso hated commissions. And the one he received early in 1937, from the Republican government of Spain for a canvas for its Paris World's Fair pavilion, proved no exception.

The bombing of the Basque city of Guernica on April 26, 1937, by 43 German planes, a bombing that killed better than 20 percent of Guernica's 7,000 citizens, galvanized him into action. Picasso worked with relentless fury until he finished the huge canvas in less than a month.

The resulting painting, Guernica, is now at the Reina Sofia Museum in Madrid, after decades at the Museum of Modern Art. A few of the preliminary studies can be seen at the Guggenheim as a component of the current blockbuster, "Picasso and the War Years: 1937-1945," on view until May 9, 1999.

Guernica has never stopped being the emblematic painting of the horrors of war. Today, its name stands in equal measure for the city and the art work. Its grayness, the crying woman, the disembodied bull's head with pointed tongue, all have become widely understood anti-war icons.

Picasso's penultimate anti-war painting, The Charnel House (1945-46), is part of the Guggenheim exhibition. This commemoration of the atrocities of the German concentration camps is strong and memorable, though it does not pack the emotion of Guernica. "Its grisaille harmonies distantly echo the black and white of the newspaper images but, more crucially, establish the proper key for a requiem," wrote MoMA curator William Rubin about this work.

"I did not paint the war," Picasso is reported to have said, in the autumn of 1944, "because I am not one of those artists who go looking for a subject like a photographer, but there is no doubt that the war is there in the pictures which I painted then."

A visit to the Guggenheim provides an ideal chance to look for the war in Picasso's paintings of the period. Making frequent appearances are skulls -- in combination with still lifes, weeping women and interiors. In these works, Picasso brings the dialogue between death's head and still life up to a life-and-death pitch.

His most agonizing depictions of the skulls comes from the early war months, starting October 1939. They are blood red, gray and black with teeth bared against an unseen enemy. These culminate in the haunting skull sculpted in bronze and copper (1941?).

Later skulls (1945) are softened by their coloration, only to haunt us again in an ink and charcoal drawing, now in the collection of the Musée Picasso, Paris.

The curators of the Guggenheim show, Steven A. Nash (chief curator at the Fine Arts Museums of San Francisco, where the exhibition has already appeared) and the Guggenheim's own Robert Rosenblum, argue that the war casts its shadows across these ordinary images. The ferocity of war is foreseen in the painting Cat Seizing a Bird (1939), for instance. Or Night Fishing at Antibes (1939), which shows two men spearing fish at night aided by a powerful lantern, is said to allegorically refer to sudden death coming from above.

Picasso made more than 100 drawings for Man with a Lamb (1943), the evocative life-size bronze that the Guggenheim uses as the final work in the exhibition. Picasso's work is equivocal, stern and tortured but loaded with religious connotations of forgiveness and compassion. The work remained in the center of Picasso's studio until well after war's end.

During the war, Picasso stayed in Paris, like thousands of other Frenchmen. Whether this was out of courage or passivity or some other reason remains unclear. He was 59 years old when the Germans entered the city in June 1940. He did not leave France for the U.S. or Mexico, even though both issued invitations (the idea of Picasso as a New York exile seems inconceivable now -- how did it seem then?).

Picasso's ties were to his adopted country and the three women who functioned in his orbit: Marie-Therèse Walter, the pliant blonde who bore him a child; Dora Maar, the intellectual photographer with the black mane and the ferocious eyes; and waiting in the wings, 21-year-old Françoise Gilot, who would always take him with a grain of salt.

Picasso would hold court every day at a Spanish restaurant, the Catalan, near his Grands-Augustins studio. Here he was able, despite rigid ration restrictions, to feast on chateaubriand and drink his Pernod, surrounded by friends like his publisher Ambroise Vollard, his secretary Jaime Sabartés, the photographer Brassaï and Julio González, who helped Picasso master the intricate secrets of metalworking and welding.

As an artist classified as a "degenerate Bolshevik," Picasso faced obstacles. He only had one minor show in a mediocre Paris gallery during the war years, but his work appeared frequently in group shows and did very well at auction. He was openly maligned by collaborationist artists like Maillol, Derain, Vlaminck and van Dongen.

There were many contradictions in his life at this time. He had to register for possible transport to Germany for slave labor. Yet, on the other hand, he appeared to have been greatly aided by Arno Breker, Hitler's favorite sculptor, who made certain that Picasso had the necessary metals to cast his sculptures, even though the Germans were melting down Parisian statues for their war effort. Breker apparently also helped by securing necessary alien residency permits.

During the occupation, some 75,000 Nazi victims were executed in the region of Paris. Among the French intellectuals who died were Robert Desnos, Otto Freundlich and Max Jacob. Many more artists escaped France for the United States and elsewhere, including Marc Chagall, Marcel Duchamp, Fernand Léger, Alberto Giacometti and Max Ernst.

All in all, Picasso took the middle road, being neither a collaborationist nor a resistance fighter.

A beautifully illustrated catalogue, with essays by Nash, Rosenblum and five other scholars, accompanies the exhibition. The dual chronology compiled by Nash, with its parallel entries marking the process of the war next to events in Picasso's life and career, provides the most chilling answer to the question, What did you do during the war, Picasso?