A leading figure of the Spanish and Argentinian anarchist movement both as a theorist of anarcho-syndicalism and an important actor in the Spanish Civil War (1936-1939). He has written on this event and on Argentinian anarchism. His works are in Spanish.
Born in Reyero, in the Province of León, in Spain, on May 20, 1897, he emigrated to Argentina at the age of 8 with his parents, Donato García Paniagüa and Angela Fernández.
He returned to Spain in 1912 and was a student until 1915 at the University of Madrid.
In 1917, he was imprisoned for a year and a half on account of his participation in a strike. Thereafter, he returned to Argentina.
He became active in the Argentinian anarcho-syndicalist Federación Obrera Regional Argentina (FORA) and edited its daily newspaper La Protesta. He rejected the conception of an all-encompassing union and considered that this institution had to defend the workers, fight for liberty and disappear with the advent of an anarcho-communist society.
He represented the FORA at the Berlin meeting in 1922 in which was created the new International Working Men’s Association (IWMA). He started medical studies in Berlin, where he met his future wife, Elise Kater, the daughter of a publisher. However, he interrupted his studies at the request of some friends and left Germany in 1926 to participate at the foundation of the Mexican Confederación General de Trabajadores (CGT) and returned to Argentina where he resumed the publication of La Protesta and edited also another newspaper, La Antorcha .
This was to be a short experience: Abad de Santillan was condemned to death in 1930 for his antistatist ideas. He escaped to Uruguay, but returned to Argentina where he lived as a clandestine and published several works. However, in 1933 he returned to Spain and settled in Barcelona.
He joined the Federación Anarquista Ibérica (FAI), and in 1935 became the secretary of the Peninsular Committee. He edited Tierra y Libertad and founded another newspaper, Tiempos Nuevos 1935-1936. After July 19, 1936 he joined the antifascist militias in Catalonia. On December 1936 he was became the Minister of Economy of Catalonia.
Shortly before the fall of Barcelona, in 1939, he took refuge in France and then settled in Argentina were he lived again as a clandestine and edited the Gran Enciclopedia Argentina.
He returned to Barcelona in 1977, where he lived till his death, on October 18, 1983.