The Spanish Civil War was fought between the democratically-elected government (with others and support from the Soviet Union) and the rebels against this government, lead by General Francisco Franco, a nationalist, supported by Italy and Germany.

It's not a simplification to say the war was fascism vs democracy, but also not entirely true. Two of the superpowers of Europe, Britain and France, were liberal democracies and they resolved not to get involved militarily. So in this capacity, two powerful democratic states chose to resign from intervening against fascism. Some leading figures in these democratic countries, like British Foreign Secretary Anthony Eden were unclear from time to time on how far they actually supported the democratically-elected Republican government. In Britain and the Spanish Civil War, Tom Buchanan writes:

Eden's policy on Spain evolved considerably during the Civil War, although primarily in response to the actions of Germany and Italy rather than as a consequence of personal sympathy for the Spanish Republic.

Britain's policy of appeasement which it had been pursuing for some time now, and was applied in international crises like Hitler's remilitarisation of Rhineland, the rearmament of Germany and the Italian invasion of Abyssinia acted as an impediment for any serious British or French action. Britain felt Germany was as or more powerful than they were, and did not want to risk a war with them in Spain. Similarly, although feeling far greater sympathy for the Republicans, Leon Blum of France ultimately agreed with non-intervention to appease the fascist dictatorships for fear of their power.

The British Prime Minister, Stanley Baldwin, treated the Spanish Republican government with even more contempt when he told the Labour Party that any expression of sympathy with the Republican government would at such a time be against British interests and unpatriotic.

Quite crucially, the Soviet Union was a major actor in the Spanish Civil War. The communist ideology spread by the USSR was obviously an immediate threat to the ruling classes of countries like Britain as it was to Hitler, or as Hitler was to Britain. This can be seen in a common phrase at the time: "better Hitlerism than communism".

Thanks to the British and French's arms embargo on the Spanish government, their only plentiful source of military material was the Soviet Union. Soviet sources claim 2,000 citizens fought in Spain for the Republican government, no small number.

There was also the volunteers who fought for the Republican side. 53,980 volunteers from 55 countries fought in the International Brigades during the war, mostly all communists. Other groups who fought alongside the Republicans came from groups like the P.O.U.M (Partido Obrero de Unificacion Marxista, also communists) and the Confederacion Nacional de Trabajo (an anarcho-syndicalist trade union, also of the far-left). Thus, it was easy to paint the Republic as a front for communism.

Thus, the democratic governments which held major international power were not in unity with the Republican government in Spain. Ultimately, from a geopolitical perspective, it was not as simple as "democracy vs fascism", but rather democracy vs fascism vs communism.

Sources

• Britain and the Spanish Civil War, by Tom Buchanan, Cambridge University Press (1997)
• The Battle for Spain: The Spanish Civil War 1936-1939, by Antony Beevor (2012)
• Homage to Catalonia, by George Orwell (1938)