information:classification
International Brigades

On 26 July, just eight days after the revolt had started, an international communist conference was held at Prague to arrange plans to help the Republican Government. It decided to raise an international brigade of 5,000 men and a fund of 1 billion francs. At the same time communist parties throughout the world quickly launched a full-scale propaganda campaign in support of the Popular Front. The Communist International immediately reinforced its activity sending to Spain its leader Georgi Dimitrov, and Palmiro Togliatti the chief of the Communist Party of Italy. From August onward aid started to be sent from Russia, over one ship per day arrived at Spain's Mediterranean ports carrying munitions, rifles, machine guns, hand grenades, artillery and trucks. With the cargo came Soviet agents, technicians, instructors and propagandists.

The Communist International immediately started to organize the International Brigades with great care to conceal or minimize the communist character of the enterprise and to make it appear as a campaign on behalf of progressive democracy. Attractive names were deliberately chosen, such as Garibaldi Battalion in Italy, the Canadian "Mackenzie-Papineau Battalion" or Abraham Lincoln Battalion in the United States.

Many non-Spaniards, often affiliated with radical communist or socialist entities, joined the International Brigades, believing that the Spanish Republic was a front line in the war against fascism. The units represented the largest foreign contingent of those fighting for the Republicans. Roughly 40,000 foreign nationals fought with the Brigades, though no more than 18,000 were in the conflict at any given time. They claimed to represent 53 nations.

Significant numbers of volunteers came from France (10,000), Nazi Germany and Austria (5,000), and Italy (3,350). More than 1,000 each came from the Soviet Union, the United States, the United Kingdom, Poland, Yugoslavia, Czechoslovakia, Hungary and Canada. The Thälmann Battalion, a group of Germans, and the Garibaldi Battalion, a group of Italians, distinguished their units during the siege of Madrid. Americans fought in units such as the XV International Brigade ("Abraham Lincoln Brigade"), while Canadians joined the Mackenzie–Papineau Battalion.

More than 500 Romanians fought on the Republican side, including Romanian Communist Party members Petre Borilă and Valter Roman. About 145 men from Ireland formed the Connolly Column, which was immortalized by Irish folk musician Christy Moore in the song " Viva la Quinta Brigada ". Some Chinese joined the Brigades; the majority of them eventually returned to China, but some went to prison or to French refugee camps, and a handful remained in Spain.