5 Ways the Spanish Civil War Set the Stage for World War II

During the Spanish Civil War, Franco counted on the support of large sections of the military, landholders, business leaders, fascists, the Catholic Church and those who wanted to restore the monarchy, which had been abolished in 1931. Opposing him was a coalition of Soviet-backed communists, anti-Stalin Marxists, socialists, anarchists, regional separatists and pro-democracy moderates.

The pro-Franco Nationalists hoped to destroy Spain’s nascent democracy and “return to an older, rigidly hierarchical” society dominated by the army, the church and large landowners, says Helen Graham, a historian of modern Europe at Royal Holloway, University of London, and the author of multiple books on the Spanish Civil War, including The Spanish Civil War: A Very Short Introduction. The anti-Franco Republicans, on the other hand, wanted Spain to be “more socially and economically inclusive,” Graham says. Other Spaniards tried to stay out of the conflict altogether.

While the various pro-Franco factions remained largely united, the Republicans suffered from deep internal divisions. This “civil war within the civil war,” as it’s sometimes called, reached its peak in May 1937, when clashes left hundreds dead in Barcelona following a police raid on the anarchist-controlled central telephone exchange.

Many of the political and economic ideologies at play during the Spanish Civil War, such as fascism, communism and democracy, would loom even larger during World War II.

The July 1936 uprising put Franco and his cohorts in control of the conservative heartland in southern and western Spain. But the Republican government retained some two-thirds of the country, including Madrid, Barcelona and other big cities. The coup, Graham says, seemed to be failing, that is, until Nazi Germany and Fascist Italy jumped to Franco’s rescue. Without their intervention, Graham says, “there would have been no actual battlefield war in Spain at all.”

Within days of the civil war’s outbreak, German and Italian planes began airlifting Franco’s troops over from Spanish Morocco, thereby overcoming a Republican naval blockade. Germany and Italy likewise provided high-grade warplanes, tanks, arms and, in Italy’s case, over 70,000 troops. (The Germans, by contrast, sent some 20,000 military personnel, and Portugal sent a few thousand soldiers as well.)

All this support proved of great benefit to Franco. For example, in the type of air raid that would become commonplace during World War II, Germany’s Luftwaffe bombed the town of Guernica—an episode immortalized in a Pablo Picasso painting—and other nearby areas as part of a successful Nationalist campaign to conquer the Basque region in 1937.

“After the Nationalists take the Basque region, it’s really hard to see the Republicans winning the war,” says Wayne H. Bowen, a professor of history at the University of Central Florida and the author of several books on 19th- and 20th-century Spain.

Bowen points out that Benito Mussolini and Adolf Hitler weren’t necessarily destined to be allies, and that tensions existed over, among other things, their competing designs in Austria and the Balkans. But the Spanish Civil War “really helps crystallize that partnership,” he says. “They see their own interests much more closely aligned. They have the same enemies, the same friends and the same goals.”

From 1937 to 1940, Germany and Italy signed a series of agreements involving themselves and Japan that formed the basis of the Axis alliance. (At the time, Japan was in the midst of its own conflict that prefigured World War II: a brutal invasion of China.) Germany and Italy would remain roughly equal partners until around 1941, Bowen says, by which time Hitler’s military successes and Mussolini’s military failures made it clear that Germany was the “big dog” and Italy the “subordinate.”

In addition to using Spain as a testing ground for military weapons and tactics, Hitler and Mussolini hoped to challenge Britain and France, then the world’s leading imperial powers. Much to their surprise, their intervention on Franco's behalf met minimal resistance. Though fully aware of Germany’s and Italy’s military intervention, Britain pursued a nonintervention policy that, in practice, amounted to an “arms embargo solely operating against the Spanish Republic,” Graham says.

“The Republic was defeated by the British-imposed arms embargo even more than it was by Nazi and Fascist intervention,” Graham says, adding that it “could never sustain military offensives for very long.”

In turning a blind eye, British Prime Minister Neville Chamberlain—who was far from alone among British elites in distrusting the Spanish Republic—hoped in part to limit domestic protests over the aerial bombardment of Spanish civilians. In a 1938 Cabinet meeting, for example, Chamberlain suggested “that a verbal request needed to be made to Franco that if he must bomb Barcelona please could it occur more ‘discreetly,’” Graham says.

While Britain maintained its nonintervention policy toward Spain, Chamberlain likewise stood by as the Nazis annexed Austria and then occupied Czechoslovakia. Despite the prime minister’s assurances that he had secured “peace for our time,” Britain and France finally declared war following the German invasion of Poland in September 1939. “Had Britain taken a different line in Spain, pushing back earlier against Nazi and Fascist intervention there (as Hitler and Mussolini had expected) then everything might have played out differently,” Graham says.

Of course, Britain did not remain militarily idle during the Spanish Civil War. As Bowen points out, it used that period to expand and modernize its military, including ramping up production of the Spitfire and Hurricane fighter planes that helped Britain fend off German attacks during the Battle of Britain.

None of the civil war’s major battles spilled beyond Spain’s borders. Nonetheless, it was in some respects a global conflict. Even as Germany, Italy and Portugal supported the Nationalists, the Soviet Union—and to a lesser extent Mexico—supplied the Republicans, albeit with largely antiquated and overpriced weapons. “The Republicans got far less from the Soviet Union than the Francoists got from Germany,” Bowen says.

Other countries, including the United States, officially remained neutral. But that didn’t stop more than 35,000 anti-fascist volunteers from some 60 countries—or roughly four-fifths of the sovereign nations then in existence—from flocking to Spain to fight the Nationalists. (Many were recruited through the Communist International, an association of national communist parties.) Though most volunteers in the International Brigades hailed from Europe, with the largest contingent from France, others journeyed from as far away as Brazil, China and Australia. They included Jewish refugees from Nazi Germany and some 2,800 Americans who joined the so-called Abraham Lincoln Brigade.

Among the members of the Abraham Lincoln Brigade were hundreds of American Jews worried about the rise of antisemitism in Europe, along with at least 90 Black Americans, including Oliver Law, who in 1937 became the first Black American to command white troops in combat. Vaughn Love, another Black volunteer, later said, "We didn't know too much about the Spaniards, but we knew that they were fighting against fascism, and that fascism was the enemy of all Black aspirations."

When the Spanish Civil War ended, some International Brigades volunteers fled to France along with hundreds of thousands of other refugees and joined the French Foreign Legion or French Army—and later the Free French resistance movement. For certain Republican veterans of the Spanish Civil War, Bowen says, “there’s only a brief pause before they’re once again in uniform, once again fighting the Germans.” Some former Abraham Lincoln Brigade members, meanwhile, went on to serve in the Office of Strategic Services (OSS), the predecessor to the CIA, using contacts and skills gained during the Spanish Civil War to assist anti-Hitler resistance movements across Europe.

Some die-hard Republican veterans even returned to Spain after World War II in a failed attempt to revive the fight against Franco. “They don’t occupy any territory, they don’t take over any regions,” Bowen says. “They’re almost all captured, killed or retreat back to France.”

Though far fewer in number than those in the International Brigades, around 1,000 to 1,500 volunteers from Ireland, France, Russia, Romania and elsewhere joined Franco’s Nationalist forces. Many of these men were fascists, monarchists, antisemites, devout Christians or some combination thereof, motivated in part by opposition to communism. Franco preferred to deny their existence, instead depicting his movement as purely Spanish and the Republicans as corrupted by foreign influences. Few Americans are known to have fought with Franco, though Texaco’s Norwegian-born American CEO, Torkild Rieber, supplied the Nationalists with oil on favorable terms in violation of U.S. neutrality laws.

Despite his sympathies for Hitler and Mussolini, Franco kept Spain out of World War II. Even so, Nationalist veterans of the Spanish Civil War were among the nearly 50,000 Spanish volunteers who served in the Blue Division, fighting alongside German forces against the Soviet Union.

Early in the Spanish Civil War, Nationalist forces massacred up to 4,000 alleged Republicans in the town of Badajoz. Similar massacres occurred in Málaga, Toledo and elsewhere, with the support or approval of Nationalist military leaders, one of whom urged his followers in a radio broadcast “to kill like a dog anyone who dares oppose you.” Among those executed in 1936 was playwright and poet Federico García Lorca.

Republicans committed myriad atrocities as well, including the murder of thousands of Catholic clergy and members of religious orders, as well as the execution of more than 2,000 suspected Nationalist sympathizers outside Madrid. “The concern for civilian populations was nowhere near the top of anyone’s list,” Bowen says. “To a certain extent both the Republicans and the Nationalists hoped to terrorize the other side into submission.”

Though estimates vary widely, historian Paul Preston concluded in his 2012 book The Spanish Holocaust that some 200,000 people were executed behind the lines over the course of the conflict—roughly the same number as died in battle—with the Nationalists responsible for around 150,000 of those deaths. Still more soldiers and civilians died from hunger, in bombing campaigns or in prison. Another 20,000 or so perceived opponents were then shot to death by the Franco regime following the war’s conclusion. On the whole, Bowen says, the Nationalists practiced “organized oppression,” and the Republicans engaged in “revolutionary chaos.”

In many ways, the violence in Spain foreshadowed the far more extensive violence to come in World War II. Yet Bowen draws a distinction between Franco and Hitler. “What you don’t really see in Spain is attempts to wipe out entire populations,” he says. For example, “they don’t set out to kill every Basque. They want them to speak Spanish and be loyal to the Franco regime, and that’s enough.”