In August 1936 Harry Pollitt arranged for Tom Wintringham to go to Spain to represent the CPGB during the Civil War. While in Barcelona he developed the idea of a volunteer international legion to fight on the side of the Republican Army. He wrote: "You have to treat the building of an army as a political problem, a question of propaganda, of ideas soaking in."
On 10th September 1936 Wintringham wrote to Harry Pollitt that he had arranged for Nat Cohen, a Jewish clothing worker from Stepney, to establish "a Tom Mann centuria which will include 10 or 12 English and can accommodate as many likely lads as you can send out... I believe that full political value can only be got from it (and that's a lot) if its English contingent becomes stronger. 50 is not too many."
Maurice Thorez, the French Communist Party leader, also had the idea of an international force of volunteers to fight for the Republic. Joseph Stalin agreed and in September 1936 the Comintern began organising the formation of International Brigades. An internatinal recruiting centre was set up in Paris and a training base at Albacete in Spain.
Battalions estblished included the Abraham Lincoln Battalion, British Battalion, Connolly Column, Dajakovich Battalion, Dimitrov Battalion, Mackenzie-Papineau Battalion, George Washington Battalion, Mickiewicz Battalion and Thaelmann Battalion.
A total of 59,380 volunteers from fifty-five countries served during the Spanish Civil War. This included the following: French (10,000), German (5,000), Polish (5,000), Italian (3,350), American (2,800), British (2,000), Canadian (1,000), Yugoslavian (1,500), Czech (1,500), Canadian (1,000), Hungarian (1,000) and Scandinavian (1,000). These men were organized into the 11th, 12th, 13th, 14th and 15th of the Mixed Brigades.
Men who fought with the Republican Army included George Orwell, André Marty, Christopher Caudwell, Jack Jones, Len Crome, Oliver Law, Tom Winteringham,