He then lived with Françoise Gilot, first in Antibes and then in Vallauris, until she left him in 1953. After the liberation of Paris he joined the Communist Party. Throughout World War II Picasso remained in Paris, although the occupying Nazis forbade him to exhibit. He had left his wife in 1935 and his new mistress, Marie-Thérèse Walter, bore him a daughter, Maïa. Meanwhile he had bought a chateau at Boisgeloup in 1932, where he produced large iron sculptures and plaster heads.
Picasso never returned to Spain after that year. This painting expressed protest and horror at the bombing of a Basque town by fascist forces in 1937. Images of violence and anguish became increasingly dominant from 1928 and culminated in Picasso's huge masterpiece, Guernica (1937). After 1925 the calmness of his earlier pictures gave way to a sense of convulsive movement, as in The Three Dancers (1925), and he began to exhibit with surrealists. As well as pictures in the cubist manner, Picasso produced many neoclassical figure paintings. The following year he married the ballerina Olga Koklova, who bore his son Paul in 1921. The partnership with Braque ended in 1914 when Braque enlisted in the army, and in 1917 Picasso left for Rome to design costumes and scenery for Diaghilev's Ballets Russes. Its first stage – analytical cubism – provided artists with new ways of representing visual reality its second stage – synthetic cubism – included the use of collage and established the concept that a picture no longer had to mirror the world but could exist in its own right. This was the most revolutionary aesthetic movement of the century. It heralded the cubist movement, which from 1909 Picasso developed in close collaboration with Georges Braque, whom he had met in 1907, and with Juan Gris after about 1912. This tendency can be seen as early as 1906 but it was in 1907 that he shocked even the most avant-garde artists of his circle by the violent simplification and distortion of the human form in his Les Demoiselles d'Avignon, which can now be seen as a turning point in European art. The Cézanne memorial exhibition of 1907 and a growing interest in African masks and carvings inspired him to concentrate on the analysis and simplification of form during the years 1907–09, sometimes called his ‘negro period’. In 1904 he settled in Montmartre, and began to paint the less austere pictures of his ‘rose period’ (1905–06) in which acrobats, dancers, and harlequins were represented in pinks and greys. The paintings of his ‘blue period’ (1901–04) used melancholy blue tones to depict the poor, the suffering, and the outcast. Showing a prodigious talent from an early age, he ran through a wide variety of styles in Barcelona until he visited Paris in 1901. He signed his earliest paintings with both surnames but dropped his father's name after about 1900. Picasso was born in Malaga, the son of José Ruiz Blanco, an art teacher, and Maria Picasso. Because of his prolific inventiveness and his technical and expressive brilliance he dominated avant-garde art in the first half of the twentieth century and is usually considered the greatest modern artist.