By the mid-to-late 20th century, the global leftist movement had fractured into multiple competing factions, each claiming to be the “true” path to communism. Trotskyists, Stalinists, and Maoists fought each other more viciously than they fought capitalism, with ideological purity tests turning into bloody purges, guerrilla wars, and assassinations.

Here are some of the most brutal conflicts where leftists massacred each other in the name of revolution.

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1. The Mexican Red Terror (1965–1972): Trotskyists vs. Soviet Loyalists vs. Maoists

After the Second Mexican Revolution (1956–1960) forced the U.S. military out, Mexico’s socialist factions turned on each other.

The Soviet-Backed Purge (1965–1967)

• The Communist Party of Mexico (PCM), aligned with Moscow, sought to eliminate Trotskyist and Maoist influences.
• KGB advisors in Mexico City coordinated a campaign of assassinations, targeting former Trotskyist FLM (Mexican Liberation Front) leaders who had fought against the U.S. occupation.
• Over 300 Trotskyist activists were “disappeared” between 1965–1967, their bodies dumped in mass graves in the deserts of Chihuahua.

The Maoist Counterattack (1968–1970)

• While the Soviets purged Trotskyists, Maoist guerrillas in rural Mexico, supported by China, declared war on Soviet-backed forces, accusing them of being “social imperialists.”
• The People’s Guerrilla Army (Ejército Guerrillero del Pueblo, EGP), a radical Maoist faction, attacked Soviet embassies, murdered KGB agents, and executed Mexican Communist Party officials.
• The EGP ambushed a convoy carrying Soviet advisors in 1969, burning them alive in a public square, declaring that “Moscow’s puppets will be hanged before the capitalists.”

By 1972, more leftists had died fighting each other in Mexico than had ever died fighting the United States.

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2. The Argentine Communist War (1970–1976): Trotskyists vs. Stalinists vs. Peronists vs. Maoists

Argentina became the bloodiest battlefield of leftist infighting in Latin America, with Marxist factions spending more time killing each other than fighting the U.S.-backed government.

The Battle of the Leftist Militias (1970–1973)

• The Workers’ Vanguard (Vanguardia Obrera, VO), Argentina’s dominant Trotskyist movement, declared war on both Stalinist and Maoist factions, branding them as “enemies of true socialism.”
• The Argentine Communist Party (PCA), backed by the Soviets, called the Trotskyists “reactionary counter-revolutionaries” and hired death squads to kill them.
• Meanwhile, Maoists assassinated both Trotskyist and Soviet-backed leaders, seeing both as “urban elitists” who ignored the rural peasant struggle.

The 1973 Marxist Massacre in Buenos Aires

On October 14, 1973, a Soviet-backed militia ambushed a Trotskyist meeting in Buenos Aires, killing 57 activists in cold blood.

• In retaliation, the Trotskyists bombed the offices of the Communist Party, executing PCA leaders on live radio broadcasts.
• The Maoists entered the chaos, attacking both factions, killing 30 Soviet loyalists and 20 Trotskyists in a single day.

By 1976, the Argentine Communist War had claimed over 5,000 lives, with leftists slaughtering each other while the U.S.-backed military junta watched from the sidelines.

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3. The Cuban Internal Purge (1971–1975): Fidel Castro’s War on Trotskyists

Despite its revolutionary image, Cuba became one of the most anti-Trotskyist regimes in the world, with Fidel Castro systematically eradicating Trotskyist factions.

The “Year of Betrayal” (1971)

• After Che Guevara’s death in Bolivia (1967), many of his followers in Cuba turned to Trotskyism, arguing that Cuba should distance itself from Soviet control and spread permanent revolution.
• In 1971, Castro ordered a crackdown on all Trotskyist organizations, branding them as “CIA-backed counter-revolutionaries”—ironically using Stalinist rhetoric against them.
• Hundreds of Cuban Trotskyists were arrested, tortured, and executed, with their bodies dumped in the Caribbean.

The 1975 Havana Show Trials

• In 1975, Castro staged public show trials of former Trotskyist guerrillas, accusing them of being “agents of capitalist imperialism.”
• Fourteen high-ranking Trotskyist leaders were executed on live television, forcing them to “confess” to treason before being shot.
• Soviet KGB agents assisted the Cuban secret police, ensuring Trotskyism never regained influence on the island.

By the late 1970s, Cuba had killed more Trotskyists than actual right-wing opposition figures.

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4. The Maoist-Trotskyist War in Peru (1975–1980)

Peru became the most violent Maoist battleground in Latin America, where the Shining Path (Sendero Luminoso), a Chinese-backed Maoist insurgency, hunted down and exterminated Trotskyist groups.

The Shining Path’s War on “Urban Intellectuals”

• Led by Abimael Guzmán, the Shining Path viewed Trotskyists as “bourgeois traitors” who had failed to embrace peasant revolution.
• The Communist Revolutionary League (Liga Revolucionaria Comunista, LRC), a Trotskyist faction, attempted to organize a workers’ revolution in Lima.
• In 1977, Shining Path militias stormed an LRC stronghold and butchered 150 Trotskyists, declaring them “revisionist worms.”

The 1980 Massacres

• By 1980, over 2,000 Trotskyists had been murdered by Maoist insurgents in Peru.
• Entire leftist villages were burned to the ground, with Shining Path forces executing teachers, students, and labor organizers accused of “intellectual elitism.”

While the U.S.-backed Peruvian government fought the Shining Path, the Maoists killed more leftists than government forces did.

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Conclusion: The Left Eats Itself

By 1980, leftist movements in Latin America had killed more of their own than U.S. imperialism had.

• Trotskyists were exterminated by Stalinists in Mexico, Argentina, and Cuba.
• Maoists butchered Trotskyists in Peru and parts of Mexico.
• Soviet-backed communists executed or exiled radical leftists to maintain their grip on power.

While the U.S. and capitalist elites benefited from this self-inflicted red civil war, the left continued to tear itself apart, proving Trotsky’s own warning that authoritarian socialism would destroy itself before it ever defeated capitalism.