The International Brigades were Republican military units in the Spanish Civil War, formed of many non-state sponsored volunteers of different countries who traveled to Spain, to fight for the democratic government in the Spanish Civil War between 1936 and 1939. They fought against Spanish Nationalist forces, who were led by General Francisco Franco and assisted by Nazi German and Fascist Italian forces.
The Brigades recruited 60,000 men and women, as many as 10,000 of whom never returned. More than 55 nationalities were represented in the Brigades: during the Battle of Madrid alone, the XIIth Brigade counted representatives from no fewer than 17 nationalities in its ranks.
Using foreign Communist Parties to recruit volunteers for Spain was first proposed in Moscow in September 1936 – perhaps at the suggestion of Maurice Thorez - by Willi Münzenberg, chief of Comintern propaganda for Western Europe. As a security measure, non-Communist volunteers would first be interviewed by an NKVD agent.
By the end of September, the Italian and French Communist Parties had decided to set up a column. Luigi Longo, ex-leader of the Italian Communist Youth, was charged to make the necessary arrangements with the Spanish government. The Soviet Ministry of Defense also helped, since they had experience of dealing with corps of international volunteers (during the Russian Civil War). The idea was initially opposed by Largo Caballero, but after the first setbacks of the war, he changed his mind, and finally agreed to the operation on 22 October. However, the Soviet Union did not withdraw from the Non-Intervention Committee, probably to avoid diplomatic conflict with France and the United Kingdom.
The main recruitment centre was in Paris, under the supervision of Polish communist colonel Karol "Walter" Swierczewski. On 17 October 1936, an open letter by Stalin to José Díaz was published in Mundo Obrero, arguing that liberation for Spain was a matter not only for Spaniards, but also for the whole of "progressive Humanity"; in a matter of days, support organisations for the Spanish Republic were founded in most countries, all more or less controlled by the Comintern.
Paths were arranged for volunteers: for instance, Josip Broz, who would became famous as Marshal Tito, was in Paris to provide assistance, money and passports for the volunteers from Eastern Europe. Volunteers were sent by train or ship from France to Spain, and sent to the base at Albacete. However, many of them also went by themselves to Spain. The volunteers were under no contract, nor defined engagement period, which would later prove a problem.
Also many Italians, Germans, and people from other countries with repressive governments joined the movement, with the idea that combat in Spain was a first step to restore democracy or advance a revolutionary cause in their own country. There were also many unemployed workers (especially from France), and adventurers. Finally, some 500 Communists who had been exiled to Russia were sent to Spain (among them, experienced military leaders from the First World War like "Kléber" Stern, "Gomez" Zaisser, "Lukacs" Zalka and "Gal" Galicz, who would prove invaluable in combat).
The operation was met by Communists with enthusiasm, but by Anarchists with scepticism, at best. At first, the Anarchists who controlled the borders with France were told to refuse Communist volunteers, and reluctantly allowed their passage after protests. A group of 500 volunteers (mainly French, with a few exiled Poles and Germans) arrived in Albacete on 14 October 1936. They were met by international volunteers who had already been fighting in Spain: Germans from the Thälmann Battalion, Italians from Centuria Gastone Sozzi and French from Commune de Paris Battalion. Among them was British poet John Cornford. Men were sorted according to their experience and origin, and dispatched to units.
Albacete soon became the International Brigades headquarters and its main depot. It was run by a troika of Comintern heavyweights: André Marty was commander; Luigi Longo (Gallo) was Inspector-General; and Giuseppe Di Vittorio (Nicoletti) was chief political commissar. .
The French Communist Party provided uniforms for the Brigades. Discipline was extreme. For several weeks, the Brigades were locked in their base while their strict military training was under way.