[2] In August 1936 he joined the Sébastien Faure battalion in the Durruti Column and went to fight against the Francoists on the Aragon Front in the Spanish Civil War.

[2] Unwilling to perform military service in Belgium, in around 1931 he moved to Paris where he made contact with the "Anarchist Union".

[1] Before the end of 1936, however, Mercier-Vega had returned to France where he launched a massive campaign of information and support in respect of the Spanish republic.

[5] Following deep differences, both over organisation and the role of "factory groups" in industrial confrontations and over the importance of the Spanish Civil War, Mercier-Vega quit the Anarchist Union in November 1937.

[7] He tried, unsuccessfully, to embark from Marseilles and then, supported by activist networks, made his way to Brussels where he was accommodated by Hem Day.

The Germans never conquered the French imperial territories in Africa, however, and on 26 June 1942 Mercier-Vega signed up as a volunteer with the Free France (government in exile) organisation which was commanded, mostly from London, by Charles de Gaulle.

[10] During his career he worked with the libertarian press on the creation of several reviews, such as " Révision" (1938) with Marie-Louise Berneri, "Aportes" (1966-1972) and "Interoogations" (1974-1979).