Rosenberg, Léonce (1877–1947) and Rosenberg, Paul (1881–1959). French art dealers, brothers. In 1906 they took over the Paris gallery of their father, Alexandre Rosenberg, who had set up in business in 1872, specializing first in Old Masters and later in Impressionist and Post-Impressionist pictures. However, in 1910 they split the business, and for the next few years Léonce was primarily a collector rather than a dealer. He returned to dealing during the First World War, when
Kahnweiler's forced absence in neutral Switzerland allowed him to become the main advocate of
Cubism by giving contracts to
Braque,
Gris, and
Léger. In 1918 he opened the Galerie de l'Effort Moderne, which for a few years was a powerful force in promoting avant-garde art. Between 1924 and 1927 it issued the
Bulletin de l'Effort Moderne (40 issues), which provided a forum not only for his own views, but also, for example, for those of Giorgio de
Chirico, Theo van
Doesburg, and the critics Maurice Raynal (1884–1954) and Pierre Reverdy (1889–1960). Soon after the war, however, several of the leading artists Rosenberg represented (including
Picasso) went over to his brother Paul, and Léonce made himself unpopular in the early 1920s when he acted as an expert for the French government's liquidation of Kahnweiler's confiscated pre-war stock; this outraged many people in the art world, as it gave Rosenberg ‘a chance to liquidate the stock of his commercial rival at knock-down prices and take advantage of his privileged position to expand his own’ (catalogue of the exhibition ‘The Essential Cubism', Tate Gallery, London, 1983). During the 1930s his business was badly hit by the Depression.
Paul Rosenberg's gallery was very up-market and he concentrated on promoting established artists rather than fostering new talent. Picasso (1918), Braque (1922), and Léger (1927) all moved from Léonce to Paul, and in 1936 he also became
Matisse's dealer. In the period between the world wars he maintained a branch of his gallery in London, and in 1940 he moved his business to New York, where his son Alexandre acted as manager.