Unleashed on 17 July 1936 by a military coup against the democratically elected government of the Second Republic, the Spanish civil war was a rehearsal for the second world war. The British, French and American governments stood aside and permitted General Francisco Franco, with the substantial aid of Hitler and Mussolini, to defeat the republic. To this day, the war is remembered by many as “the last great cause”, the war of the volunteers of the International Brigades, of the bombing of Guernica and of the mini-civil war within the civil war fought in Barcelona as CNT anarchists and the Poum’s quasi-Trotskyists battled forces of the Catalan government, the Generalitat, backed by the communists of the PSUC.

Eighty years ago this week, the Ramblas of Barcelona echoed with gunfire. Much of what happened on the streets during the May days is well known thanks to George Orwell’s Homage to Catalonia, but not why it happened. Herbert Matthews, the great New York Times correspondent, summed up the consequent problem: “The book did more to blacken the loyalist cause than any work written by enemies of the Second Republic.” This is unfortunate since, for many thousands of people, Homage to Catalonia is the only book on the Spanish civil war that they will ever read.

An eyewitness account of two fragments of the war, the book presents two priceless pieces of reportage: the first a vivid account of the experiences of a militiaman on “a quiet sector of a quiet front” in Aragón, evoking the fear, the cold and, above all, the squalor, excrement and lice of the rat-infested trenches; the second a vibrant description of several days and nights spent on the roof terrace of the Poliorama theatre in the Ramblas while defending the Poum HQ across the street. Orwell’s account of the poisonous atmosphere in Barcelona during and after the May days of 1937 is invaluable, but marred by its assumption that the Stalinist suffocation of the revolution would lead to Franco’s eventual victory.

Homage to Catalonia belongs in any list of important books on the Spanish civil war. It has informed opinion in the English-speaking world about the war – providing the inspiration, for instance, for Ken Loach’s Land and Freedom. However, limited to the time and place of Orwell’s presence in Spain, it would certainly not be there as a reliable analysis of the broader politics of the war, particularly of its international determinants. He clearly knew nothing of its origins or of the social crisis behind the Barcelona clashes. In none of his writings does he mention having any prior acquaintance with Spain or ever reading a book in Spanish about the war or anything else. Orwell himself acknowledged “my partisanship, my mistakes of fact, and the distortion inevitably caused by my having seen only one corner of events”.

Amendments to what he had written in Homage to Catalonia were reflected in his writings after later conversations in London with the exiled Spanish republican prime minister, Dr Juan Negrín. In answer to his questions about the wider issues of the civil war, Negrín explained why the republic had been forced to turn to the Soviet Union as the only great power prepared to sell weaponry. He also outlined the problems of trying to fight a war while dealing with “the motley conglomerate of incompatible parties, labour unions and dissident groups, and also the frequently self-appointed, largely unconstitutional, local and regional ‘governments’”. Negrín concluded that Orwell was “idealistic and weltfremd [unworldly]”.

Perhaps he was not so unworldly. He had introduced himself to Negrín only as “an editorialist of the Observer” without mentioning his links with the Poum. Maybe he was uncomfortable with the association. He wrote to a friend in December 1938: “I’ve given a more sympathetic account of the Poum ‘line’ than I actually felt … because it has had no hearing in the capitalist press and nothing but libels in the leftwing press.” That spirit of fair play led to Orwell brushing over the Poum’s undermining of the republic. It seems irresponsible, given that he admitted that, prior to the May events, he was trying to transfer from the Poum to the International Brigades. That meant that he sympathised with the view of socialists, liberal republicans and communists that an effective war effort required state control of the economy and the mass mobilisation of a modern army.

He was in the Poum only because he had been rejected by Harry Pollitt, the secretary-general of the British Communist party. So he arrived in Barcelona with Independent Labour party credentials. Taken to the Poum’s Lenin barracks in the Gran Vía, he was welcomed because of his literary celebrity. Orwell was not popular among fellow British militiamen, who, like Pollitt, resented his “cut-glass Eton accent”. One said he disliked the “supercilious bastard” on sight: “He really didn’t like the workers.” He had been exhilarated to find “a town where the working class was in the saddle”, but the collectivist experiments of autumn 1936 had not created a war machine. The May events were about removing revolutionary obstacles to the war’s efficient conduct. He acknowledged this in his 1942 essay Looking Back on the Spanish War: “The Trotskyist thesis that the war could have been won if the revolution had not been sabotaged was probably false. To nationalise factories, demolish churches, and issue revolutionary manifestos would not have made the armies more efficient. The fascists won because they were the stronger; they had modern arms and the others hadn’t.”

However, in his book he expressed pro-revolutionary views based on ignorance of the damaging impact on the republic’s international image of the atrocities committed against priests, landowners and merchants in Lérida by the Poum and in eastern Aragón by anarchist columns from Barcelona. For instance, he completely misunderstood the notorious case of Antonio Martín Escudero, an anarchist smuggler who controlled the area of the French-Catalan Pyrenean frontier known as La Cerdanya. There, he and his group carried out acts of banditry, atrocities against the clergy and the extortion of people crossing into France. At the end of April, he was killed at the small town of Bellver in a clash with local people determined to end his reign of terror. Orwell accepts the anarchist version that portrayed Martín as a martyr murdered by forces of the Generalitat.

In Barcelona, social and political hostilities had been mounting for some months. The tension that Orwell encountered when he arrived in April was not the result of communist malevolence but of economic and social distress. The Catalan population had been swollen by the arrival of 300,000 refugees. The strain of housing and feeding a 40% increase in Barcelona’s population had embittered existing conflicts. Until December 1936, when the CNT had controlled the supply ministry, the anarchist solution had been to requisition food in the countrysid. As farmers hoarded stocks to sell on the black market, this provoked shortages and inflation. Then the PSUC took over the supply portfolio and implemented a more market-based approach. This infuriated the anarchists but did not solve the problem. There were bread riots in Barcelona, and armed clashes for control of food stores between anarchists and the PSUC.

That conflict was just one aspect of a much more serious one. The Poum’s call for a revolutionary workers’ front with the CNT was debilitating the war effort. Moreover, the Poum’s entirely justified public criticisms of the Moscow trials were seen as treacherously undermining the republic’s relationship with its only powerful ally. To secure Russian arms deliveries, the Poum leader, Andreu Nin, was removed in a cabinet reshuffle on 16 December. However, hostility to the anti-Stalinist left was not just about pandering to the Russians. Many Catalan anarchists were not committed to the war effort. In mid-March, several hundred anarchists who had opposed the militarisation of the militias abandoned the front and took their weapons to the Catalan capital. The revolutionaries had 60,000 rifles in Barcelona. They refused either to give them up or to go to the front themselves to fight. It was only a matter of time before outright conflict would break out. Orwell, given his lowly position in a Poum militia, saw none of this.

As clashes grew more violent in Barcelona, the Generalitat prohibited the traditional May Day rallies, which was perceived as a provocation by the CNT rank and file. In early May the crisis exploded. The immediate catalyst was the Generalitat’s seizure of the CNT-controlled central telephone exchange in Barcelona on 3 May after an anarchist operator had interrupted a telephone call by the president of the republic, Manuel Azaña. In the wake of deteriorating conditions and police heavy-handedness, elements of the CNT – supported by the Poum – confronted the forces of the Generalitat and the PSUC. The anarchists could win only by recalling their troops from Aragón. Then they would have to fight both the central republican government and the Francoists. Accordingly, with the approval of the anarchist ministers, decisive police reinforcements from the government in Valencia began to arrive on 7 May. Hundreds of CNT and Poum militants were arrested, although the needs of the war industries limited the scale of the repression. Andreu Nin was murdered by a squad of NKVD agents. Initial revolutionary achievements were steadily dismantled.

After a nightmarish experience on the run in Barcelona, Orwell wrote “Curiously enough, the whole experience has left me with not less but more belief in the decency of human beings.” He never abandoned his commitment to the Spanish republic. Back in London, in July 1937, he wrote: “The International Brigade is in some sense fighting for all of us – a thin line of suffering and often ill-armed human beings standing between barbarism and at least comparative decency.” And yet Orwell’s book makes it too easy to forget that the Spanish republic was defeated by Franco, Hitler, Mussolini, and the self-interest and pusillanimity of the British, French and American governments. His ignorance of the wider picture while in Spain was forgivable. The problem is rather that his judgments facilitated the book’s subsequent use as part of a cold war narrative. Instructions left before his death for a later edition ignored his acceptance of the need for a unified war effort in Spain. It is as if the Orwell of Animal Farm, Nineteen Eighty-Four and the lister of suspect fellow-travellers for the Foreign Office thought that he should let it stand as another nail in the communist coffin, despite its distortion of the Spanish situation.

Paul Preston is a professor at the London School of Economics and the foremost historian on the period