The following lecture was delivered by Alejandro López, a writer on Spain and other topics for the World Socialist Web Site, at the SEP (US) International Summer School, held August 2-9, 2025. It is the final part of a three-part lecture on the Great Terror in the Soviet Union during the 1930s. Part 1 is posted here and Part 2 here.

The WSWS is also publishing two writings by Leon Trotsky on Spain to accompany this lecture: “The Lesson of Spain — A Last Warning” and “The class, the party, and the leadership.” We encourage our readers to purchase the compilation of Trotsky’s writings on Spain, “The Spanish Revolution (1931-39)” from Mehring Books.

The Spanish Revolution was a decisive turning point not only in Spain’s history but, above all, for the international working class. It was a central front in the global struggle between revolution and counterrevolution. The Spanish Civil War was, above all, a revolution betrayed. My contribution follows two essential presentations. Comrade Katja has outlined the purges of the Comintern, and comrade Fred has exposed the political genocide of old Bolsheviks carried out through the Moscow Trials. Both these events deeply intersect with the Spanish Civil War.

The Stalinist bureaucracy intervened to forestall revolution in Spain, launching a murder campaign against anyone even suspected of political links to Trotsky. The machinery of repression built in Moscow and refined in the Comintern was exported to Spain. Lies about “Trotskyite conspiracies” and “counterrevolutionary plots” fabricated by Stalin’s secret police in the USSR were used to crush the Spanish Revolution. Spain became a testing ground of counterrevolution. Ramón Mercader, Trotsky’s future assassin, was trained in this lethal task during the Spanish Civil War.

The Spanish Revolution stands as one of the most powerful revolutionary uprisings of the 20th century. For a time, the emergence of a second workers state after the October Revolution in Russia was a real possibility. The revolution inspired workers across the world, from Europe and the US to China. A revolution in Spain would have transformed the political situation globally. And that is precisely why the Soviet bureaucracy intervened to stop it.

The election of the Popular Front

The Spanish Revolution erupted in 1931 with the fall of the monarchy and the proclamation of the Republic unleashing a revolutionary crisis that deepened over the next five years. Events confirmed Trotsky’s perspective of Permanent Revolution: The Spanish bourgeoisie, politically bankrupt and fearful of working class opposition, proved incapable of satisfying any of the democratic and social tasks posed by the revolution.

Between 1931 and 1936, Spain was gripped by deepening economic and social crisis, marked by escalating class struggle. The Republic’s early reforms, like limited land redistribution, secularisation, and labour reforms, were met with fierce resistance from the elites: the Church, the Army, and the landlords. The bourgeoisie, tied to the old order, proved incapable of carrying out even the most basic reforms. Spain remained mired in extreme inequality: two million landless labourers lived in destitution, while 50,000 landowners controlled half the land. In the south, braceros, or landless rural labourers, toiled for starvation wages on vast estates; in the north and east, peasants were crushed by debt, with many forced into wage labour. The industrial working class, though relatively young, was concentrated in Catalonia and the Basque Country and highly militant. The 1929 Great Depression further intensified the crisis, plunging the economy into contraction and deepening poverty.[1]

The working class and peasantry, whose expectations of real change had been raised by the fall of the monarchy, were increasingly radicalised by the Republic’s failure to deliver. In January 1936, the Popular Front was formed as an electoral alliance between bourgeois republican parties and workers’ organisations, including the social-democratic Socialist Party (PSOE), the tiny Stalinised Communist Party, a faction of the anarcho-syndicalist National Confederation of Labor (CNT), and the centrist Workers’ Party of Marxist Unification (POUM). The leadership of the CNT, while maintaining its formal abstentionist stance, encouraged its members to vote for the Popular Front.

Although most workers were in the CNT, significant layers supported the PSOE, particularly in Castille and the Basque Country, and the POUM. The latter was led by former Left Oppositionist leader Andreu Nin, who had broken with Trotsky to support the Popular Front, and Joaquin Maurin, leader of the Workers and Peasants Bloc (BOC).

The POUM’s role was deeply contradictory. Though it emerged from the revolutionary tradition of the Left Opposition, it abandoned the fight for the independence of the working class by entering the Popular Front. Politically, the POUM occupied a centrist position, wavering between revolution and reform. While opposing Stalinism, it refused to draw the necessary conclusions about the counterrevolutionary nature of the Popular Front. This centrist vacillation made it a chief obstacle to the independent mobilisation of the working class. Despite this, as we shall see, the Stalinists launched a vicious campaign against the POUM, precisely because it could give voice, however confusedly, to revolutionary opposition within the working class, and for fear that it could re-establish links to Trotskyism.

Amid an eruption of class struggle, the Popular Front was elected in February 1936, forming a government led by moderate republicans. Every city and province of any importance had at least one general strike during the following months, with millions of workers participating. But the Popular Front government failed to meet the demands of the working class and rural poor. “The capitalists,” wrote American Trotskyist Felix Morrow in Revolution and Counterrevolution in Spain, “concluded that democracy was intolerable, and that meant that bourgeois democracy and reformism were finished in Spain.”[2]

The coup leaders made no attempt to hide their genocidal intentions. In May 1936, Gen. Emilio Mola, the coup’s chief organiser, declared: “The action must be extremely violent as soon as possible to reduce the enemy, which is strong and well-organised […], applying exemplary punishment to those individuals in order to strangle rebel movements or strikes.” Two days after the coup began, he made it even more explicit: “It is necessary to spread terror, eliminating without scruples or hesitation all those who do not think as we do.... All those who oppose the victory of the movement to save Spain will be shot.” Franco himself was equally blunt. When asked by a journalist if controlling all of Spain would mean killing half its population, he replied without hesitation: “If that’s what’s necessary, that’s what will be done.”

But the Franco’s hopes of rapid victory proved a serious miscalculation, as the working class rose up in revolutionary struggle against it.

The July 1936 Revolution

On July 17, 1936, the Army took the city of Melilla in Spain’s North African enclave, calling on all military garrisons to rise up against the Popular Front government. Prime Minister Casares Quiroga, asked by journalists what he was going to do about the coup, complacently joked: “They have arisen? Good. I am going to bed.” Casares refused to deliver arms to the workers’ organisations as the military uprising unfolded. The next day, on July 18, the military rebellion spread to all of Morocco, the Canary Islands and to Seville on the Spanish mainland.

The coup did not come as a surprise. The Popular Front government had prior knowledge of the coup, having been alerted to unusual military drills in Morocco and northern Spain weeks before. Franco had even been moved to the Canary Islands, to deprive him of access to his troops in Melilla. However, the Popular Front government kept this information from the workers, fearing that it would fuel the revolutionary movement of the masses.

In Catalonia, workers organised under the anarcho-syndicalist CNT had prepared systematically ahead of the coup, organising 20,000 workers in neighbourhood defence committees. Workers had mapped troop movements, located weapons shipments, and planned their response. When the coup began, they erected barricades, cut communications, mobilised trucks and declared a general strike. On July 19, workers demanded weapons from the Catalan government. The Catalan government refused.[3]

Despite this, by July 20, the armed working class had defeated the Army in Catalonia. Workers in Madrid, Valencia, Bilbao and Gijón followed the lead of the workers in Barcelona. The Asturian miners sent a column of 5,000 dynamiters to Madrid to assist. In Malaga, the workers initially had no arms and used petrol to set fire to barricades surrounding the military barracks.

In words of historian Agustín Guillamón who has covered Spain’s July days extensively, “The workers, posted in the vicinity of the barracks, had orders to sound the alarm but not to engage the soldiers until they came very close to the city center. The previously determined tactic of the Confederal Defense Committee foresaw that it would be easier to fight the troops in the streets than if they remained entrenched in their barracks.”[4]

Workers showed in deeds their readiness for socialist revolution. They expropriated factories, buildings, and land; armed, organised, and transported militiamen; formed patrols against fascist provocateurs; resumed factory production without managers; and requisitioned vehicles and food supplies. Borders and ports were placed under the control of workers’ committees, and in the Navy, where 70 percent of the officers were killed by their men, authority was exercised by sailors’ committees. If comrades want to understand the revolutionary atmosphere of those times, one of the best descriptions was captured in George Orwell’s famous Homage to Catalonia.

It was the first time that I had ever been in a town where the working class was in the saddle. Practically every building of any size had been seized by the workers and was draped with red flags or with the red and black flag of the Anarchists; every wall was scrawled with the hammer and sickle and with the initials of the revolutionary parties; almost every church had been gutted and its images burnt. Churches here and there were being systematically demolished by gangs of workman. Every shop and cafe had an inscription saying that it had been collectivised; even the bootblacks had been collectivized and their boxes painted red and black.[5]

The existing capitalist state institutions were reduced to an empty shell, with the machinery of government collapsing at both local and national levels as real power passed into the hands of the workers. But this collapse was partial. The capitalist state had not been smashed. It continued to exist, however weakened, as a parallel structure. The Popular Front was, in Trotsky’s words, the shadow of the bourgeoisie. Its authority was deeply challenged, its control over the territory severely eroded, yet its apparatus, including ministries, police, courts, remained intact, waiting for an opportunity to reassert itself. The failure to smash the capitalist state machine and replace it with a workers’ state was not a secondary detail but a deadly danger. A revolution that leaves the capitalist state standing, even in ruins, leaves open the road to counterrevolution.

It is essential to briefly examine the international situation. Typically, the Spanish Civil War is narrowly framed within the national context, writing off the struggle for world socialist revolution. A common argument is that the global balance of forces in the 1930s was far less favourable to the Spanish Revolution than it had been to the Russian Revolution.

This claim is demonstrably false. In France, the Popular Front government of Léon Blum, backed by Stalinist parties, was turning against the working class following the powerful May–June general strike. In the United States, a massive strike wave was laying the foundations for the rise of industrial unionism. In the USSR, mass anger was building among workers against Stalin’s 5-year plans, one of the reasons he launched the Purges. In Greece, on the other side of the Mediterranean, there was a powerful strike movement from April to August 1936.[6]

And in Germany, Hitler had come to power just three years earlier, crushing the Communist and Social Democratic workers’ organisations. Yet, there was increased dissatisfaction in this period over the widening gap between prices and wages, which pushed workers’ incomes down to starvation levels despite falling unemployment, whilst farmers, small producers and traders were no longer able to sell their goods at a profit due to the introduced price scales. Historian Peter Longerich quotes reports of the Gestapo “according to which parts of the old Marxist-minded labour force [in Germany] had by no means discarded their former convictions, indeed, as a result of the undesirable developments of recent times, ‘Marxist’ tendencies were again becoming virulent among the labour force and even the communist temptation was luring them.”[7]

A successful revolution in Spain would have sent shockwaves around the world. The revolutionary potential in Europe and beyond was far from exhausted. A victorious socialist revolution in Spain could have ignited struggles across the continent and reshaped the global class struggle, offering a powerful counter-offensive against fascism and Stalinism alike.

Permanent Revolution versus Counter Revolutionary Stalinist Popular Frontism

Two opposing strategies confronted each other in Spain. One was the proletarian revolutionary socialist line based on Permanent Revolution. Trotsky, writing from exile in Mexico, explained:

The revolutionary army must not only proclaim but also immediately realize in life the more pressing measures of social revolution in the provinces won by them: the expropriation of provisions, manufactured articles, and other stores on hand and the transfer of these to the needy; the redivision of shelter and housing in the interests of the toilers and especially of the families of the fighters; the expropriation of the land and agricultural inventory in the interests of the peasants; the establishment of workers’ control and soviet power in the place of the former bureaucracy.[8]

The Army’s loyalty to Franco was far from secure. The 80,000 Moroccan troops in the Army of Africa had no genuine stake in defending Spanish imperialism. In the Spanish countryside, the peasants, many of whom were forcibly conscripted in territories seized by the military, had been fighting for land reform since the proclamation of the Republic in 1931. Studies of Franco’s Army reveal an officer corps deeply suspicious of its own rank and file. The conscripted peasant soldiers were seen as unreliable and were subjected to brutal discipline to force them into submission. The mass execution of leftists also terrorized the conscripted.[9] Yet the Popular Front government made no attempt to undermine Franco’s social base, refusing to give land to the peasants or self-determination to Morocco.

The committees that emerged were organs of revolutionary proletarian power with the potential to develop into soviets, like those that arose in revolutionary Russia in 1917. The Trotskyist vanguard, however, was numerically weak and, from the outset, faced the obstacle posed by Stalinism and the POUM joining the Popular Front. The issue was that turning these organisations into the basis of workers power required the building of a powerful revolutionary vanguard in the working class. As a result, despite their immense power and initiative, these bodies remained fragmented and localised, lacking the cohesion and leadership needed to unify their efforts and establish a workers’ state, which could only come to power through smashing the existing capitalist state.

The other strategy was the Stalinist Popular Front, which aimed to block a socialist revolution and dissolve all forms of workers’ self-organization that threatened the capitalist state. But blocking the revolution meant physically eliminating anyone on the left who represented an actual or potential opposition to the Popular Front government. While Stalinism had previously betrayed workers’ struggles based on its nationalist theory of “Socialism in One Country,” the Popular Front marked its transformation into a consciously counterrevolutionary force. Preserving the alliance with bourgeois parties and imperialist France and Britain required the suppression of the revolution.

This counterrevolutionary programme was spelled out in a letter to Prime Minister Francisco Largo Caballero (PSOE) signed by Stalin, where he urged the Spanish government to protect private property, win over the urban and rural middle classes, and avoid any appearance of communism so as not to alarm Britain and France:

The petty and middle urban bourgeoisie should be attracted to the government side and be given at least the chance to occupy a neutral position, which would favour the government, by protecting it from attempts at confiscation and securing as far as possible the freedom of trade.” The bourgeois Republican party “should not be repulsed, but on the contrary, should be drawn in, brought nearer and associated with the common exercise of government. It is especially important that the government should secure the support of [President of the Republic and leader of the Republican party] Azaña and his group and that everything should be done to help them in overcoming their vacillation. This is necessary in order to prevent the enemies of Spain from regarding it as a communist republic and to forestall their intervention, which would constitute the greatest danger to the republic of Spain.” And there should be no confiscation of “the property rights and the legitimate interests of those foreigners in Spain.[10]

PCE leader José Díaz explicitly opposed Moroccan independence, proposing instead “democratic colonialism.”[11]

These strategies reflected different class orientations. On one side stood the working class, striving for a socialist revolution to defeat fascism, but confronting the dead weight of its leadership, all of which defended the Popular Front strategy. This went from the Stalinist PCE to the social democratic PSOE, the anarcho-syndicalist CNT and the centrist POUM.

Only small minorities stood in opposition to this strategy. These included the official Trotskyist Bolshevik-Leninists led by Grandizo Munis, factions of the POUM, who called for a Revolutionary Workers’ Front based on workers’ councils, and CNT militants organised in the Friends of Durruti Group, who opposed the anarchist leadership’s collaboration with the Popular Front. Though in the minority, they expressed the revolutionary will of the working class.

On the other side stood Stalinism, which gave voice to the middle classes. As Burnett Bolloten details in his meticulous The Spanish Civil War: Revolution and Counterrevolution, the PCE became the political refuge of small manufacturers, tradesmen, artisans, prosperous farmers and big landowners, groups that no bourgeois republican dared openly represent in the revolutionary atmosphere of July 1936. The PCE’s membership ballooned from 40,000 to over 90,000 within months, largely by championing private trade, opposing collectivisation, and defending property against workers’ militias.[12] “Thus, from the outset”, writes Bolloten, “the Communist Party appeared before the distraught middle classes not only as a defender of property, but as a champion of the Republic and of orderly processes of government.”[13]

The CNT and the POUM refused to seize power, choosing instead to hand it back to the Popular Front government, politically disarming the working class. Revolutionary momentum was diverted under the banner of “anti-fascist unity,” while Stalinism worked methodically to suffocate the revolution under the guise of defending it.

Andreu Nin, an internationally respected revolutionary well known to the Spanish and international working class, capitulated by joining the Popular Front government in Catalonia as Minister for Justice. Nin had a long revolutionary reputation: He attended the founding congress of the Red International of Labour Unions in 1921, served as its assistant secretary, joined the Communist Party of the Soviet Union and was elected to the Moscow Soviet. Expelled in 1928 for supporting Trotsky, he was saved from prison only by his reputation. Upon returning to Spain in 1930, he founded the Spanish Left Opposition. His stature remained so great that in 1934, amid the mass radicalisation of the working class following Hitler’s rise to power, the 60,000-strong Socialist Youth invited him to join them in the task of “bolshevizing” the party.[14]  

As Trotsky wrote at the time, “The former Spanish ‘Left Communists’ have turned into a mere tail of the ‘left’ bourgeoisie. It is hard to conceive of a more ignominious downfall”.[15]

The bloody Stalinist suppression of the revolution

Stalin’s intervention in Spain was driven not by a commitment to antifascism, but by fear, fear of war with Germany and, more decisively, fear of revolution. Initially, Stalin hoped that France would take responsibility for aiding the Spanish Republic. During the critical first six weeks of the conflict, he did nothing, instead signing the Non-Intervention Pact with Britain and France to reassure the Western powers, whose support he sought for a policy of collective security against Nazi Germany.

Yet, as the Spanish working class began to carry out insurrectionary measures intolerable to the bourgeoisie, such as expropriating property, confiscating foreign-owned companies, seizing border controls and arming themselves, Stalin’s overriding priority became the suppression of the revolution. A workers’ government in Madrid posed a direct threat to the Stalinist bureaucracy in the Soviet Union, raising the spectre of a political revolution at home. The very suggestion by the POUM of inviting Trotsky to Spain was enough to provoke panic in Moscow. The Soviet bureaucracy’s role in Spain must therefore be understood as a calculated effort to strangle the revolution, eliminate its leadership, terrorise the working class and prevent the spontaneous insurgency from developing into a politically conscious socialist movement.

One of the most striking characteristics of the documents that emerged from the Soviet archives over the past decades is the persistent anxiety they express about Trotsky and Trotskyism. It was not just Trotsky as an individual that concerned the Kremlin, but the spectre of social revolution that he personified. The name of Trotsky had become “a terminological convenience,” as he himself explained, for that much feared revolution.[16]

The first reports to come back from Moscow’s Comintern representatives in Spain alerted the Kremlin to the rapid advance of the working class. From September 1936, the Stalinist secret police, the GPU, established a station within the Spanish ministry of interior. It was led by Alexander Orlov. His role was to help the Communist Party build its own security and intelligence services that would be used to crush the working class and physically murder the left wing of the Popular Front.[17] One of the first telegrams back to Moscow shows that they were closely monitoring the revolutionary situation in Barcelona and working with the PCE leadership and the Comintern representatives to prepare for an action against the “enemies.” “The Trotskyists organization POUM, active in Catalonia,” the report claimed, “can easily be liquidated.”[18]

During the eight months after the July 1936 coup, the Stalinist-led counterrevolution gradually strangled the organizations the Spanish working class had built in response to the coup. In the name of “discipline” and defence of the “democratic republic,” the PCE, backed by the GPU, waged a systematic campaign to disband and crush workers’ factory committees and militias. The culmination of this process was the bloody suppression of the Barcelona May Days of 1937.

Between the months following July 1936 and the May Days of 1937, a series of decisive political and military measures dismantled the organs of workers’ power, restored the authority of the capitalist state and laid the groundwork for the violent suppression of revolutionary forces. The following chronology highlights key turning points in this counterrevolutionary process:

• Late July–August 1936—The PCE begins calling for “discipline” and defence of the “democratic republic,” opposing collectivization and workers’ control. The anarcho-syndicalist CNT and centrist POUM join the Catalan government, legitimising the bourgeois state and marking the first step in subordinating the revolution to the Popular Front.
• September 1936—The Stalinists enter the central Popular Front government. With backing from the Soviet Union and its military aid conditioned on suppressing revolutionary developments, they push for the full restoration of bourgeois order and the rebuilding of the capitalist state apparatus.
• October–December 1936—The Catalan government starts issuing decrees to regulate and undermine workers’ control. In the countryside, Stalinist-led forces attempt to reverse peasant collectivisations. Soviet GPU agents led by Orlov arrive in Spain alongside Soviet arms, solidifying Stalinist influence in political and military affairs.
• December 1936—The Stalinists begin a campaign of slander and repression against the centrist POUM, labelling it a “Trotskyist-fascist” organisation. An editorial in Pravda on the 17th of December 1936 declared that in Catalonia the “cleaning up of Trotskyism and Anarcho-syndicalist elements … will be carried out with the same energy as in the USSR.” In the same months, workers’ militias are forcefully incorporated into the regular Republican army, dismantling workers’ self-organisation and independent command structures. The Comintern informs the PCE that “the Trotskyites are carrying on destructive work behind the lines of the Republican army in the interests of fascism, the Presidium endorses the line of the Party for the complete and final crushing of Trotskyism in Spain, which is necessary to obtain victory over fascism.” Nin is expelled from the Catalan government at the demand of Soviet Union.
• January 1937—Moscow ordered its representatives in Spain to “launch a campaign among the masses and in the press against Trotsky and Trotskyists as terrorists and saboteurs… spies liaising with the German Gestapo.”
• March–April 1937—Tensions rise in Catalonia as the Stalinists and the Catalan government prepare to forcibly disarm workers. The Catalan Stalinist PSUC escalates attacks on POUM and the CNT positions, aiming to reassert state authority and crush dual power.
• March 1937—Trotsky issues a stark warning: “If this [collaboration with the Popular Front] policy continues, the Catalan proletariat will be the victim of a terrible catastrophe comparable to that of the Paris Commune of 1871.”

Trotsky’s warnings were confirmed in the bloody events known as the May Days of 1937. Most academics treat the May Days in Barcelona 1937 as a minor episode in the Spanish Civil War. In reality, casualties during the May Days—500 killed and 1,000 wounded—were greater that in the first week of the military uprising in Barcelona on July 19, 1936.

In early May, Republican police under Stalinist direction launched a military assault on the Barcelona Telephone Exchange, which had been under workers’ control since the start of July 1936. It was a calculated strike at the heart of workers’ control. The exchange had enabled workers to monitor and intercept government communications. The atmosphere was explosive. Just days earlier, CNT militants had been killed near the French border in a government-backed operation to retake control of the frontier. On May 1st, the government banned May Day demonstrations fearing armed worker demonstrations.

The assault on the Telephone Exchange sparked a working class uprising that would last for seven days. Workers in Barcelona, determined to defend the revolution, erected barricades and seized much of the city, which was effectively in the hands of the workers. British warships anchored offshore and Catalan President Lluis Companys begged the central government to send the Air Force to bomb the CNT headquarters in Barcelona.

A joint meeting of the POUM, CNT, FAI and Libertarian Youth executives was held that night of the 4th to decide what to do. As one of the leaders of the POUM, Julián Gorkin, later recalled, he posed the question to the CNT: “We must make our choice; revolution or counterrevolution.”[19] The POUM chose the latter.

The GPU working with the Popular Front’s secret police and the PCE went into action. Camillo Berneri, an Italian CNT member critical of the Popular Front, was murdered, as was CNT youth leader Alfredo Martinez. Freund, a German Trotskyist known as Moulin, who was the link between the small group of Trotskyists and the Friends of Durutti, “disappeared.” This was only the beginning of the repression.

CNT and POUM leaders refused to call for the seizure of power. Nin himself admitted in a statement days after they capitulated to the Popular Front: “It would have been possible to take power, but our party, a minority force within the working-class movement, could not assume the responsibility of issuing that slogan.”[20] Yet everything indicated that, had they done so, broad masses of the working class, especially in the CNT rank and file, who were far to the left of their leaders, would have followed.

But the POUM failed to supplant the CNT leadership or present an alternative. Without revolutionary leadership, the uprising was doomed. The POUM then rationalised their impotence into a “victory” to justify ending the struggle: “Beyond any doubt it [the working class] has won a great, partial victory. It has defeated the counterrevolutionary provocation. It has won the dismissal of all those who were directly responsible for the provocation.”[21]

In the aftermath of the May Days, the Stalinists moved swiftly. Juan Negrín, a right-wing Socialist trusted by Moscow, was installed as prime minister. The POUM’s newspaper La Batalla was banned. The party itself was outlawed. Its leaders were arrested and thrown into secret prisons controlled by the GPU.

An operation led by GPU chief Orlov was undertaken to kidnap Nin. He was seized six weeks after the May defeat on June 16 and then tortured and murdered after refusing to confess to being a fascist agent. Orlov had intended to use this confession to create a Moscow-style frameup. When this failed, he was murdered. In a grotesque cover-up, GPU operatives staged a fake prison raid using German-speaking International Brigade volunteers and planted fascist badges and banknotes to give the impression that Nin had been “rescued” by the Gestapo.

“Orlov, in a frenzy, crazed by the fear of failure – a failure which could mean his own liquidation – slavered over with rage against this sick man who agonised without ‘confessing’, without implicating himself or seeking to implicate his party comrades who, at a single word from him, would have been stood up against the wall for execution, to the joy and heart-felt satisfaction of all the Russians.”[22] Nin was executed on the 20th of June 1937.

The Stalinists, with Orlov behind the scenes, then set up the Barcelona Espionage and High Treason Tribunal to obtain convictions for espionage and high treason against the various leaders of the POUM, presenting fraudulent evidence of them being agents of Franco. The Tribunal rejected this accusation and instead found them guilty of being the instigators of the events of May 1937 in Barcelona, which was just as false as the other accusation.

Across Republican-controlled areas, secret prisons run by the Stalinists and the GPU agents, known as checas, in Madrid, Barcelona and Valencia became sites of torture, forced confessions and executions. The GPU maintained an extensive network of informants and infiltrators inside the POUM. Hundreds of members and sympathisers were arrested. Dozens were executed or disappeared. Many are suspected to have been disappeared without a trace in the secret GPU crematorium in Barcelona run by NKVD agent Jose Castelo Pacheco. A Spanish PCE member, Castelo was recruited by Leonid Eitingon, who led the GPU in Barcelona and whose primary function was coordinating Soviet intelligence and security operations, particularly the suppression of workers, the POUM and the CNT. Eitingon would be one of the future organizers of Trotsky’s assassination.

In February 1938, members of the Trotskyist Bolshevik Leninists were arrested and accused fraudulently of murdering León Narwicz, a captain in the International Brigades of Polish nationality, who was infiltrated into the POUM by the Popular Front’s intelligence services. He was in fact murdered by an action group of the POUM as revenge for the murder of Nin. But the POUM did nothing to clear the Bolshevik Leninists of a murder charge they knew was false and carried the death penalty.[23]

Thousands more were driven underground or forced into exile. Spain became a testing ground for Stalinist agents and assassins. When Soviet defector Ignace Reiss was murdered in Switzerland in September 1937, his killers left behind a Spanish-made overcoat, a reminder of the reach of the GPU and its operations perfected in Spain.

The Stalinist suppression of the Barcelona working class unleashed a blood purge aimed at eliminating the most militant and politically conscious elements of the proletariat. Its purpose was to exterminate all those whom the working class associated with revolution, to decapitate its leadership and to extinguish the memory and possibility of socialist transformation.

Here are some of the most well-known victims:

• Erwin Wolf (1910–1937)—A 27-year old Czech-German Trotskyist and secretary to Trotsky’s son Leon Sedov, Wolf played a key role in refuting the accusations made at the Moscow Trials and was a central figure in the International Secretariat, which was the precursor to the Fourth International. Wolf travelled to Spain to help coordinate Trotskyist activities. We know that he was active and sent back a number of reports. He was captured by the GPU and murdered a few months after arriving in Spain.[24]

• Kurt Landau (1903–1937)—A former member of the German Communist Party and Trotskyist Left Opposition, Landau fled to Spain and worked with the POUM’s international secretariat. He was abducted in Barcelona in September 1937 by Stalinist agents and is believed to have been tortured and murdered by the GPU. His body was never found. Katia Landau, who was also arrested, suspected that her husband had been taken to the Soviet Union.[25]

• Marc Rhein—A German member of the POUM and son of the Menshevik leader Rafael Abramovich, Rhein was abducted and disappeared in 1937.

• José Robles (1897–1937)—A Spanish academic and translator of John Dos Passos, Robles was critical of Stalinist repression. Robles was executed by the GPU.

• Antonio Martín Escudero (1901–1937)—A prominent anarchist from Catalonia and military commander in the early stages of the civil war. Assassinated, he was likely targeted for his defence of the independence of workers’ militias from the Stalinist-controlled command.

The suppression of the May Days marked the crushing of the revolutionary struggle of the Spanish working class. The bourgeois state was stabilised under Popular Front colours. The workers’ committees were dismantled. And the road to Franco’s victory was cleared by the very forces that claimed to defend the Republic. When Barcelona, the heart of the revolution and stronghold of the Spanish working class, finally fell to Franco’s forces in January 1939, it did so without any serious resistance.

The outcome was a defeat of the working class that strengthened the fascist powers, paving the way for Hitler’s regime to launch the Second World War in Europe, five months after Franco’s April 1, 1939, victory speech. This war would claim 75 million lives, including six million Jews murdered by the Nazis in the Holocaust.

In Spain itself, 500,000 people died in the Civil War, out of a population of 23.6 million. Half a million were forced to flee into exile and 150,000 workers, artists and left-wing intellectuals were murdered behind fascist lines. After the war’s end, 20,000 supporters of the Republic were shot, and an estimated one million people were interned in 300 concentration camps and prisons. Franco’s regime would survive for four decades, only falling amid mass protests and strikes in 1978.

The breeding ground of Trotsky’s assassins and the Stalinist social type

The Spanish Civil War was the battleground where Stalin’s international terror apparatus took shape, and the GPU refined its methods of infiltration, provocation, torture and assassination. These methods, tested against a living revolution, would be exported across Europe, the Americas and even Asia. Figures like Ramón Mercader, the man who would murder Trotsky in 1940, were recruited, trained, and deployed during the Civil War. He also trained anti-Trotskyist spies, like English volunteer, David Crook, who after the war went to China, where he spied on suspected Trotskyists.

Mercader embodied the Stalinist social type: the bureaucratic functionary whose political identity was rooted not in revolutionary conviction that animated early Soviet spies like Ignass Reiss, but in blind loyalty to the Stalinist bureaucracy and hostility to the working class.

After the death of former Spanish Communist Party leader Santiago Carrillo, who as a youth had helped lead the campaign against the POUM during the Spanish Civil War, historian Pelai Pagès recounted a conversation he had with Carillo. At a dinner with historians, including Pagès, a discussion began about Nin’s murder and the suppression of the POUM. At the dinner, Carrillo asserted with chilling detachment: “In the 1930s, no communist militant who had been asked to kill Trotsky would have refused to do so.”[26]

Stalinism had become a consciously counterrevolutionary force. In Spain, the clash between revolution and counterrevolution was a fight to the death. Stalinism emerged from the defeat of the Spanish working class and the fascist victory in the Spanish Civil War with a global murder machine dedicated to tracking down and murdering Marxists internationally.

The lessons of Spain

The Spanish Revolution stands as one of the clearest vindications of Trotsky’s theory of Permanent Revolution, and one of the most tragic confirmations of the consequences of the working class lacking a revolutionary leadership. The Popular Front did not serve as a tool to resist fascism, but a bourgeois-Stalinist strategy for social counterrevolution. Subordinating the working class to the capitalist state, it betrayed the historic interests of the proletariat in order to defend the capitalist order. By disarming the working class politically and militarily, the Popular Front paved the way for Franco’s victory.

Fascism cannot be defeated by relying on factions of the bourgeoisie. It represents a mortal threat to the working class that can only be overcome by means of the independent political mobilisation of that class in the struggle to overthrow capitalism. As Trotsky warned, “The Spanish revolution once again demonstrates that it is impossible to defend democracy against the methods of fascist reaction. And conversely, it is impossible to conduct a genuine struggle against fascism otherwise than through the methods of the proletarian revolution. Stalin waged war against ‘Trotskyism’ (proletarian revolution), destroying democracy by the Bonapartist measures of the GPU.”[27]

The capitalist state cannot be used to carry out a socialist revolution. It must be smashed and replaced by organs of workers’ power. In Spain, the revolutionary committees and militias pointed in the direction of soviets. But the working class lacked a revolutionary vanguard capable of leading a conscious struggle for state power. The Stalinists succeeded in politically isolating and physically annihilating the most advanced elements before they could rally the working class against the Popular Front and toward socialist revolution.

Above all, Spain confirms the historical necessity of building a revolutionary party of the working class, armed with an internationalist programme and grounded in the strategic lessons of past struggles. The Fourth International, whose founding was initiated following the victory of fascism in Germany, stood alone in drawing the essential lessons of the Spanish Civil War and in waging an irreconcilable struggle against the Stalinist counterrevolution.

[1] Pierre Broué and Emile Témime, “The Revolution and the Civil War in Spain” (1961): https://www.marxists.org/archive/broue/1961/spain/rev-spain.html

[2] Felix Morrow “Revolution and Counter Revolution in Spain” (1938): https://www.marxists.org/archive/morrow-felix/1938/revolution-spain/ch01.htm

[3] Agustín Guillamón: “Barricades in Barcelona: The CNT from the victory of July 1936 to the necessary defeat of May 1937” (2006): https://libcom.org/article/barricades-barcelona-cnt-victory-july-1936-necessary-defeat-may-1937-agustin-guillamon

[4] Ibid.

[5] George Orwell, “Homage to Catalonia” (1938): https://www.george-orwell.org/Homage_to_Catalonia/0.html.

[6] See Fourth International, Volume VI, No. 2 (Whole No. 51), “Civil War in Greece”: https://www.marxists.org/subject/greek-civil-war/fourth-international/1945/02/x01.htm

[7] Peter Longerich “Unwillige Volksgenossen” [Unwilling Countrymen], 2025

[8] Leon Trotsky, “The Lessons of Spain: The Last Warning” (December 1937): https://www.marxists.org/archive/trotsky/1937/xx/spain01.html

[9] Francisco Leira Castiñeira, “Soldados de Franco” (SIGLO XXI, 2020).

[10] Communist Party of Spain, “Guerra y Revolución en Espana”, Volume ii, (Moscow, 1971), 96-97.

[11] Miguel Martín, “El colonialismo español en Marruecos” (Ruedo Ibérico, 1973), p. 178.

[12] Cited in Bolloten, “The Spanish Civil War: Revolution and Counterrevolution” (The University of North Carolina Press, 1991), p. 83.

[13] Ibid., p. 87.

[14] Pierre Broué, “The Socialist Youth in Spain (1934–1936)” (December 1983): https://www.marxists.org/archive/broue/1983/12/carrillo.html

[15] The Treachery of the Spanish “Labor Party of Marxist Unity” (22 January 1936): https://www.marxists.org/archive/trotsky/1936/01/poum.htm

[16] WSWS, “Introductory remarks by World Socialist Web Site correspondent at Madrid congress on Spanish Civil War” (11 December 2006): https://www.wsws.org/en/articles/2006/12/madr-d11.html

[17] Boris Volodarsky, “Stalin’s Agent: the life and death of Alexander Orlov” (Oxford, 2015), p. 161.

[18] Ibid., 162.

[19] Op Cit., Bolloten, p. 432.

[20] Andreu Nin, “1937. POUM. El significado y alcance de las jornadas de mayo frente a la contrarrevolución” (Barcelona, 12 May 1937) : https://fundanin.net/2018/12/03/el-significado-y-el-alcance-de-las-jornadas-de-mayo-1937/

[21] Pierre Broue “The ‘May Days’ of 1937 in Barcelona” (1988): https://www.marxists.org/history/etol/document/spain/spain04.htm

[22] Jesús Hernández, “I Was a Minister of Stalin” (1953). Excerpt can be found at: https://www.marxists.org/history/spain/writers/hernandez/persecution_of_poum.html

[23] Agustín Guillamón: “El terror estalinista en Barcelona (1938): Los informes de Gerö y Stepanov. El proceso contra la Sección Bolchevique-Leninista de España por el asesinato del capitán Narwicz” (2013): grupgerminal.org/?q=system/files/2013-2018-terrorestalinista-guillamon-0.pdf

[24] Pierre Broué, “Erwin Wolf: A Biographical Sketch” (1979): https://www.marxists.org/history/etol/revhist/supplem/wolf.htm

[25] Katia Landau, “Stalinism in Spain” (1988): https://www.marxists.org/history/etol/document/spain/spain09.htm

[26] Pelai Pagés, “Los claroscuros de una trayectoria política” (Público, 18 September 2012): https://www.publico.es/actualidad/claroscuros-trayectoria-politica.html

[27] Leon Trotsky, “The Lessons of Spain: The Last Warning” (December 1937): https://www.marxists.org/archive/trotsky/1937/xx/spain01.htm