During the Spanish Civil War Albacete was the headquarters and training camp of the International Brigades. The International Brigades were Republican military units made up of many non-state-sponsored, anti-fascist, mostly socialist and communist, volunteers from different countries that travelled to Spain to fight for the Republic in the Spanish Civil War between 1936 and 1939. An estimated 32,000 people from about 53 nations volunteered. They fought against rebel Spanish Nationalist forces led by General Francisco Franco and assisted by German and Italian forces.
The main recruitment centre was in Paris, under the supervision of Polish communist colonel Karol Świerczewski. On 17 October 1936, an open letter by Joseph 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. Entry to Spain was arranged for volunteers who 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. 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. Finally, communists who had been exiled to Russia were sent to Spain, among them, experienced military leaders from the First World War. A group of 500 volunteers, mainly French, with a few exiled Poles and Germans, arrived in Albacete on 14th October 1936. They were met by international volunteers who had already been fighting in Spain and sorted according to their experience and origin, and dispatched to units. 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.