It is more complicated than you think, but I will explain something off the bat.
As far as anarcho-communism is concerned, there are two main variants, as I see it. There are those that basically fight for the same thing as ordinary communists/Marxists, except that instead of desiring a centrally planned economy with an organized state they prefer everything to be decentralized, with no form of mercantilism or exchange. Then t here is also mutualism, which is basically market socialism/a form of capitalism but without the state where everyone is a small proprietor/small scale capitalist. As for what the Spanish anarchists were, they were very incoherent. Both strains were represented.
Also, there was no anarchist state in Spain. The Spanish anarchists mostly belonged to one organization, the CNT. The CNT was actually part of the Popular Front government along with the Socialist Party of Spain(the dominant member of the coalition), the Communist Party of Spain, the Republican Left, and the Catalonian spinoff of the Republican Left, PSUC. There were actually CNT ministers in the government. Obviously this was extremely hypocritical. Anarchists say that they want a stateless society, immediately, but the Spanish anarchists actually became an official part of the Popular Front government. A case of utopian principals clashing with reality.
When the Civil War broke out, Anarchists seized a lot of factories, especially in Catalonia, and drove a lot of landlords off their farms and collectivized them. They didn't touch foreign owned factories as they were afraid of pissing off Britain, the United States, and other foreign powers. These collectivized factories were operated to anarchist utopian principals of prioritizing quality of life of workers over efficient. In wartime conditions, this is disastrous. Production figures fell off a cliff(over 70% below pre-war levels IIRC), while in Francoist Spain arms factories' production mostly recovered to pre-war levels within about a year of the war beginning. I have to say, it was a pleasant surprise to see this represented in the game. The anarchists have a unique economy law that, while providing some bonuses, also reduces output and efficiency cap.
One thing to understand is that when the Civil War broke out, the Nationalists were mostly stopped by workers militias. The old government had mostly lost all credibility and effective power. Spain's most powerful political party, PSOE, was quasi-revolutionary and split into a liberal right wing led by Indalecio Prieto and a quasi-revolutionary wing led by Francisco Largo Caballero, who had led Spain's abortive 1934 workers revolution in Asturias. PSOE and the stalinist PCE both decided that rather than push for a Russian style revolution, that they would work to bolster the old capitalist liberal government of Spain. The PCE especially took charge of attacking the radical experiments of the anarchists and shutting down the collectivized farms and restoring property back to its old owners.
The situation was also even more complicated yet. In the chaos after the outbreak of the civil war and the near collapse of the Republican government, the anarchists emptied out most of the prisons and enlisted a lot of hardened criminals in their fighting battalions. In particular was an anarchist column called the Iron Column. It was a led by a former criminal lord arrested on charges of rape, extortion, and many such things. Anarchist squads attacked and assassinated PSOE and PCE trade union leaders, entirely unprovoked. This initiated a retaliatory cycle of violence where there was essentially a miniature civil war within the civil war going on within the Republican ranks.
It was also the case that a lot of the communications infrastructure of the Republic was held by anarchist collectivized enterprises. The Prime Minister could not even speak on the telephone without anarchists eavesdropping, and sometimes even chipping in and dropping in on the conversation. They controlled phone operations and so on. This was actually one of the big catalysts for the crackdown against the Anarchists in May 1937.
The game woefully misrepresents this. The anarchists did not rebel against the government, rather the PCE instigated a crackdown against them and violently put an end to their independent operations. The anarchists as such were not destroyed, just their influence. CNT ministers continued to serve in the government up to the very end of the war. The PCE, however, became more and more fanatical in its desire to control all political opinion within the Republic to the point of assassinating anyone even mildly critical of them, going so far as to kill other Republicans even on the field of battle!
One thing that kinda disappointed me is that we never got to see Segismundo Casado's coup in the game. It could have worked pretty well as something similar to the Fatherland Front coup we saw introduced for Bulgaria in BFTB.
The PCE's fanaticism in eliminating potential sources of internal dissent had a disastrous impact on the war effort. The PCE never was the ruling party of the Republic, rather they exercised power by proxy. The PM of the Republic after May 1937 was Juan Negrin, a member of the PSOE, was essentially a communist puppet. He even gave speeches that were literally written by Palmiro Togliatti, leader of the Italian COmmunist Party. Burnett Bulloten in his book on the Spanish Civil War provides some good evidence and a persuasive argument that Negrin's secretaries were communist spies as well.
As the war neared its end, the leaders of the PCE made many brave declarations that they would fight to the last man, and then promptly got a plane and fled to the Soviet Union. In Madrid, a Republican officer, Segismundo Casado, along with the remnants of the anarchists and other anti-stalinist officers and politicians launched a coup deposing Negrin's government to surrender to Franco. The terms of the surrender was basically unconditional surrender, with the proviso that Casado and his men and supporters in Madrid would be allowed to leave the country without interference by t he Nationalists. Surprisingly, Franco honored this promise.
Just a very brief and concise summary of some events of interest in the war. I wouldn't recommend reading online about it, tbh. The best thing you can do is pick up a book(or ideally, several of them!). The two pre-eminent historians of the Spanish Civil War in the English language are Stanley G. Payne and Paul Preston. Payne has a strong pro-franco bias and engages in borderline fascist apologetics at times, yet the depth and breadth of his mastery of the facts and his knowledge of Spanish history is unquestionable(even if his methodology and conclusions can be). Paul Preston, on the other hand, is basically the opposite. He's extremely pro-Republican and basically entire uncritical of the disastrous role played in the war by the Stalinist PCE; none the less, he's much closer to the mark in my opinion than Payne is. However, I think for the best and most comprehensive view of the history of the Spanish Civil War, you should absolutely read both.
Brief list of books I would HIGHLY recommend if you're interested in the subject:
The Spanish Civil War: Revolution and Counterrevolution by Burnett Bulloten
The Spanish Civil War: Reaction, Revolution, and Revenge by Paul Preston
The Spanish Holocaust: Inquisition and Extermination in Twentieth-Century Spain by Paul Preston.
The Spanish Civil War by Stanley Payne
The Franco Regime, 1936–1975 by Stanley Payne
I'd probably read them in that order, too. There are many more books beyond that, but I think that those will give you a pretty comprehensive view and introduction to the major subjects of interest. The anarchist question is dealt with in a lot of detail there as well. IIRC one of Payne's books goes into quite a lot of detail on it including economic figures and production numbers.
