Todos los Pueblos del Mundo están en las Brigadas Internacionales al Lado del Pueblo Español

All the peoples of the world are in the International Brigades side by side with the Spanish people, artist unknown, 1937 

As the liberal democracies refused to provide support to Spain, tens of thousands of men and women from across the world made their own way to Spain to fight against Franco. Most were recruited and organised by the Communist International and fought in the International Brigades (IB).

Over the course of the war an estimated 35,000 to 40,000 volunteers went to Spain from over 50 countries to fight Nationalist forces led by Franco, backed by Nazi Germany and Fascist Italy, while 20,000 others served in medical or auxiliary units. An estimated 15,000 volunteers died. Around 2,300 men and women went from the United Kingdom, despite government efforts to stop them, and around 500 were killed.

The IB weren’t just symbolic. They played a significant role in the war – at a time when much of the regular Spanish military had joined the uprising (choosing a side was mostly based on geography), leaving the Republic’s regular army decimated and with a weakened leadership. The International Brigades, alongside the workers militias, helped prevent Spanish democracy from almost immediate defeat while the Ejército Popular (Popular Army) was being rebuilt.

The IB volunteers were a mixture of veterans from the 1914-18 war, working class anti-fascists and exiles from Nazi Germany and Fascist Italy, unemployed, and naive middle class political idealists and intellectuals. One of the misconceptions is that British artists and writers from the middle classes made up the bulk of those who went to fight in Spain. However, Jenkins says the vast majority of those who volunteered for the International Brigades, and those who undertook a lot of the fundraising efforts, were from the working class.  

The IB took part in many of the big battles of the war, often being decisive in defensive actions; as they gained experience, they became among the most reliable troops while the regular army was being recruited and trained. They became ‘shock troops’ – thrown into the most difficult attacks and holding the line during retreats. Notably: The Jarama (Feb 1937, blocking the advance on Madrid), Guadalajara (March 1937, defeating Italian forces), Brunete (July 1937, a costly Republican offensive), Belchite (Aug-Sept 1937, another tough offensive), and the Ebro (July-Nov 1938, the Republic's last major offensive). 

The International Brigades were disbanded in September 1938, in the vain hope that the international community would pressure Italy and Germany to stop supplying Franco with troops, weapons, training and equipment.

Dolores Ibarruri said in her farewell speech on 28 October 1938:

“… For the first time in the history of the peoples’ struggles, there was the spectacle, breath­taking in its grandeur, of the formation of International Brigades to help save a threatened country’s freedom and independence – the freedom and independence of our Spanish land…. Mothers! Women! … speak to your children. Tell them of these men of the International Brigades.

Recount for them how, coming over seas and mountains, crossing frontiers bristling with bayonets, sought by raving dogs thirsting to tear their flesh, these men reached our country as crusaders for freedom, to fight and die for Spain’s liberty and independence threatened by German and Italian fascism. They gave up everything — their loves, their countries, home and fortune, fathers, mothers, wives, brothers, sisters and children — and they came and said to us: “We are here. Your cause, Spain’s cause, is ours. It is the cause of all advanced and progressive mankind…

Comrades of the International Brigades: Political reasons, reasons of state, the welfare of that very cause for which you offered your blood with boundless generosity, are sending you back, some to your own countries and others to forced exile. You can go proudly. You are history. You are legend.”

After they left Spain they had a mixed fate. Many, such as German and Italians were unable to return to their own country. Many wound up in the infamous Mauthausen concentration camp.