The ensuing irony in that era of socialist intellectuals, who wanted to run the world, running for their lives from the regimes of socialists who actually did run a good portion of it, is still lost on the People who are currently running San Francisco. Sad events all the way around.
It's replete with irony upon irony.
Perhaps the ultimate irony of it all is that the Abraham Lincoln and George Washington Battalions of the International Brigades (which is what they actually were, they were not brigade sized units in their own right) are now remembered, as here, as freedom fighters against fascism. That's simply not the case. What they were, in reality, is largely extreme left wing Americans who were "fellow travelers" with communism, if not outright communist. They weren't fighting against anything, but rather for something. The goal was to establish a radical socialist regime, which would have been effectively a Soviet style state.
Probably more than any other single group, the Americans who fought for the "Republic" in the Spanish Civil War have benefited, permanently, from the rosy glow painted on everyone who fought the Germans in World War Two. Fighting the Nazis, a worthy goal any way you look at it, was portrayed by necessity in World War Two as the equivalent of fighting against evil (which it was), and fighting for democracy. While the Nazis were truly evil, and fighting them was an absolute necessity, it's not the case that Soviet Union was fighting for liberal democracy. It was fighting for its life, and that of the Russian people, but that is not quite the same thing.
Be that as it may, when World War Two came along, the Western Allies more or less adopted a "they're just like us" propaganda position towards the Soviets. That wartime propaganda couldn't outlive the peacetime reality, so it soon became readily obvious to anyone paying attention that the Soviets were not misunderstood democrats.
But, the fact that authoritarian Franco (who was not a fascist, but who certainly wasn't a democrat by any stretch of the imagination), had received German and Italian aid right before WWII, and the fact that he more than flirted with being an Axis belligerent in WWII, pretty much caused a WWII whitewash of the Republicans, and those who supported them. That's lasted, as the Republicans lost. They ironically have the benefit of the "noble looser", which we sometimes see with other conflicts. Having never achieved power, the world was spared the executions the Republicans would have handed out, and the radical regime they would have tried to create. And we know Franco was an authoritarian. So the Republicans have been able to pretend ever since WWII that they were really not what they were.
I should note that some members of the Republicans were not extreme leftist, although their cause certainly was. And you can find examples of Republicans, both Spanish and non Spanish, who were repelled by the extremist nature of the Republican cause, or whom otherwise went on to be much less extreme in their later positions. And some members of the international brigades were either simply naive or just liked to fight. All in all, however, that doesn't change the basic nature of either sides positions in the Spanish Civil War.
The Spanish Civil War is one of those wars which has been so impacted, in historical terms, by events that came after it that it never seems to be treated in its own right, which is a shame. So many good historical texts treat it as a "precursor to WWII" that it is remembered that way. That's nonsense. The Spanish Civil War had utterly nothing whatsoever to do with Nazi Germany's absorption of Czechoslovakia, reoccupation of the Rhineland, or invasion of Poland. It wasn't a source of Nazi Germany's decision to invade the USSR (although Spain sent a division to that effort), and it had nothing to do with Hitler's post Pearl Harbor declaration of war on the US. It didn't encourage Mussolini to attack France in 1940, and the Spanish Civil War didn't convince Mussolini to attack Greece. It probably did serve to kill off a lot of radical Italian fascists, however. The Spanish Civil War didn't cause Stalin to temporarily think that Hitler was his pal, and that they could jointly carve up Poland.
The point of all that is that the Spanish Civil War, while an interesting war in its own right and period, is sui generis. It probably more closely resembles the Russian Civil War than any other war. WWII didn't go back and rearrange the war into a trial run for the Axis v. the Allies, and indeed, the foreign powers that slugged it out on Spanish turf, through the supply of volunteers and material, were proclaiming themselves to be bosom buddies shortly thereafter.