I think the factional nature of the Spanish Civil War gets overlooked partly due to the way that the two sides seemed to coalesce. The Nationalists were made up of the military and its supporters, two different stripes of Monarchists that were often hostile to each other, industrialists and large agricultural concerns that were joined in a marriage of convenience but had little in common, fascists who were often at odds with most of their ostensible allies, and much of the Catholic Church in Spain which had a number of conflicts with all of the aforementioned groups (not to mention the larger Catholic Church and its stance on the issues and groups in question). The Republicans featured multiple different groups supporting different types of communistic ideas that were often mutually hostile, groups of anarchists that were nearly as hostile to each other as they were to the communists and fascists, various democratic groups that were leery of revolution but even more leery of what they saw as fascism, unions of every type and political persuasion, advocates for regional autonomy that cared little for the revolutionary ideas of the communists and anarchists, and others. Add in the fickle Soviet support for the Republicans alongside the large Italian deployment in support of the Nationalists and the smaller but very potent German contingent supporting the Nationalists and you have an incredibly complex civil war that was less a war of two distinct sides than it was of two coalitions that were barely held together for the length of the war, as well as a kind of proxy war between the various European powers that wanted to influence the situation in Spain for their benefit while still not antagonizing potential enemies in a war that no side was quite ready to start yet. The alliances perhaps did not change as rapidly as the ones in Syria, but given the in-fighting amongst the Republican side as well as how much Franco had to suborn the various factions within the Nationalists in order to keep them in line I do think that the Spanish Civil War featured a good deal of fluidity in factional loyalty to their alliances (not to mention the bitter verbal sniping that happened after the war, especially on the Republican side).