Educated as a chemical engineer, Frank was one of the first French Trotskyists, working with surrealist Pierre Naville and the syndicalist Alfred Rosmer.

After the rise of the 1934 Popular Front government in France, Frank was a part of the faction within the movement led by his friend Raymond Molinier that remained inside the SFIO after the majority followed Trotsky's advice to leave.

Ernest Mandel comments that the group "was chiefly identified with a thorough-going preparation of anti-militarist and anti-imperialist work that earned them repression and persecution at the hands of the French imperialist government.

"[1] When the Second World War broke out, Frank was sent to Great Britain in order to continue legally publishing the movement's documents.

He was the author of a history of Trotskyism entitled The Long March of the Trotskyists and Histoire de l'Internationale communiste (1919–1943), ed.