David Korner, also known as Barta, was a Romanian Trotskyist militant. Recruited to Trotskyism as a student in Paris in the 1930s he formed the Bolshevik Leninist Group of Romania. When the Spanish Civil War and the June 1936 strikes took place he returned to France and was a member of the Internationalist Workers Party (POI). He then joined the ephemeral Workers and Peasants Socialist Party which collapsed at the start of World War II. At which point he formed the tiny Group Trotskyist. This group became the Communist Union and concentrated on doing factory work. That work came to fruition with the Renault strike of 1947 which his group helped lead and organise.

However the strains of that activity caused the group to collapse. It was briefly revived in 1950 but nothing came of it and when some former militants of the UC began publishing Voix Ouvrière in 1956 Barta was not involved. In fact there were hostile relations between Barta and the leadership of the Voix Ouvrière (now Lutte Ouvrière) group until his death.