So there are a couple of ways to take your headline question. One is in practical terms - what did Soviet intervention in the Spanish Civil War look like, in terms of aid, propaganda, military support and so on. My read of your text, however, is that you are interested more in the purpose of Soviet intervention, particularly how it related to Spanish revolutionary politics and the USSR's broader goals at the time.

To understand the thrust of Soviet policy, it's helpful to consider the role of communists - ie leftists already aligned with the USSR - in Republican Spain at the time. Before the war, the Communist Party was a significant but not massive force in Spanish politics. They had by 1936 recovered somewhat from their nadir in the early 1930s, but were far from the largest or most significant political party of the left. While they were important supporters of the electoral pact known as the ‘Popular Front’, which allowed a coalition of leftist parties to win power in the February 1936 elections, the communists were reluctant to participate directly in this new government. This reluctance stemmed partly from weakness – they were still a relatively minor party (perhaps 30,000 members and 15 or so seats in parliament after the 1936 elections) – but also because they acknowledged that their direct participation might discredit the new Popular Front government, whose main figures were initially ‘Left Republicans’ (ie liberals, broadly speaking) and (somewhat) more moderate socialists.

While it might seem strange for communists to be so circumspect, this was in line with broader international communist policy, which emphasised the building of such ‘Popular Fronts’ as a reaction to the rise of Nazism in Germany. The communists had realised that divisions on the left, particularly between German socialists and communists, had allowed Hitler to gain power and prevented them from opposing his rule until it was too late. Communists had initially expected that Hitler was the last, desperate gasp of capitalism, which would soon collapse and give them their opening for revolution. Instead, as we all know, Hitler took power and moved to stamp out political enemies, starting with the left wing political organisations. The communists realised that their priority needed to be preventing fascist governments coming to power, rather than plot their own revolutions, and the best way to do this was promote left-wing unity against fascism - both in a domestic sense, in terms of preventing fascist movements from coming to power, but also internationally, electing governments who would be willing to cooperate with the USSR in containing fascist expansionism. So, not only were the communists not in a position to launch their own revolution, it was against their immediate interests and policy to even attempt it.

So, when the question of whether or not the Spanish Civil War was a revolutionary struggle came up, communist policy was shaped by their acceptance of the Popular Front as a strategy. This meant emphasising anti-fascist unity – which given that it involved allying with moderate socialists and liberal republicans as well as those on the far left such as anarchists, was incompatible with revolutionary goals. As such, the communists consistently advocated unity in the face of the ‘fascist’ enemy, prioritising their defeat over any particular partisan programme, revolutionary or not. In other words, win the war first, worry about the revolution later. Feeding into this were concerns with the Republic's image abroad and increasing international isolation - revolutionary activity (especially violence) in the aftermath of the coup attempt had done a great deal to discredit the Republic in the eyes of potential

This put them at odds with large swathes of Spanish leftist opinion, which saw the war itself as an inherently revolutionary struggle, a revolution which had actually already taken place in areas with strong anarchist support, which saw the collectivisation of farms and factories, and the formation of revolutionary militias, in the first weeks and months of the war. This conflict framed the political tensions within the Republican camp, which boiled over at various points, most famously in Barcelona in May 1937, which saw widespread street fighting after government troops and police attempted to assert control over key local infrastructure which had been seized by revolutionary parties in the immediate aftermath of the coup attempt. While the communists backed this action, it would be misleading to label it as solely their doing. Other key Republican groups - such as the socialist PSOE or the liberal Republican Left - were much better represented in the structures of Republican governance at the time, and were also opposed to any immediate attempt at an anarchist-style revolution.

Where Spanish and Soviet communists were more obviously driving events after May 1937 was in the suppression of the POUM, a small anti-Stalinist revolutionary party, made famous due to George Orwell happening to serve in the small foreign section of their militia, and the murder of the POUM leader Andreu Nin at the hands of Stalinist operatives. Yet the narrative here is more complex than 'Soviet goons crush idealistic revolutionaries'. The POUM’s main crime in the eyes of the communists and many other Republicans was not their revolutionary ethos, but that they advocated revolution ahead of political unity and the war effort. If you look at the anti-POUM propaganda that gets spread in the aftermath of the fighting in Barcelona described by Orwell, it is this narrative that is emphasised – that the POUM was a legitimate target because they undermined the war effort, not because of their advocating revolution.

This is all not to say that communist (or Stalinist) ideology played no role. One reason that the POUM was singled out for such violent repression was their perceived connection to Trotskyism. Communists around the world had internalised anti-Trotskyist discourse by this point, and 'Trotskyite' had become a label that signified a dangerous enemy within. In the context of Spain, this meant that the anti-POUM rhetoric soon evolved from their threatening Republican unity to their being treacherous – they weren’t just disrupting unity, they were disrupting it deliberately to undermine the war effort and ensure that the fascists won, because that was the supposed ultimate goal of Trotskyists. The following passage comes from a communist-aligned periodical, just a week after fighting broke out, and shows just how swift and lethal this kind of Stalinist discourse could be:

Following months of patient explaining, the Government has finally determined to tolerate no more ‘leftist’ sabotage in the rearguard. Not sabotage alone, but thinly disguised banditry alienating the sympathies of the peasant and small trader from the Republic... Against the Fascist inspired terrorists the central Government made its hand felt, taking full responsibility for public order in Catalonia...

The hour for physical extermination of Trotskyism has arrived.

The Soviets and their Spanish adherents imported a great deal of the language and practices of Stalinist communism, which at more or less the same time was wreaking such havoc back in the USSR. But it is still far too simple to portray this as a simple betrayal of the revolution on the part of the communists – they, like most other Republicans, had adopted a pragmatic strategy in the circumstances, which emphasised unity and winning the war above all else. It’s worth noting that despite mutual suspicion, the bulk of the Spanish anarchist movement (the various major anarchist organisations were much, much larger than the POUM) never split entirely with the Republic, despite their own revolutionary beliefs. They, like others on the Republican side, accepted that the war effort came first, although they naturally disagreed with specific policies and decisions, and fought (politically) against the real and perceived encroachment of communist influence on the state, and, on the eventual defeat of the Republic, there were plenty of recriminations to go around.

(cont. below)