Karl Marx was born on 5 May, 1818, in Trier, Prussia. Two hundred and eight years later, as global inequalities sharpen and debates over empire, race and resistance rage, his legacy as a thinker who placed the struggles of colonised and enslaved peoples at the heart of the fight against capitalism deserves renewed attention. Far from a narrow Eurocentric theorist, Marx – working in close collaboration with Friedrich Engels – developed a profoundly internationalist perspective. Their writings and activism on Ireland, the 1857 Indian War of Independence, and American slavery reveal revolutionaries who saw the liberation of the oppressed as inseparable from the emancipation of the working class worldwide.Marx and Engels did not merely theorise in the abstract. They analysed concrete events, corresponded extensively with revolutionaries and thinkers, and engaged politically through journalism, the First International, and personal networks. Their evolution – from early views influenced by the era’s Eurocentric assumptions to a sharper anti-colonial stance – demonstrates intellectual honesty and a commitment to material reality. Ireland served as their primary case study of colonial domination within Europe; India illustrated the brutality and contradictions of empire in Asia; and American slavery highlighted capitalism’s reliance on racialised bondage. In each, they championed international solidarity. As Tristam Hunt argues in his biography of Engels, even when Marx and Engels expressed racialised thinking, they remained supporters of policies to reform and change the conditions of the oppressed.Ireland: England’s first colony and the ‘lever’ for revolutionMarx and Engels rightly saw Ireland as England’s oldest colony, a laboratory of racial-imperial exploitation whose subjugation propped up British power. Engels, who visited Ireland multiple times and drew on the lived experiences of his partner Mary Burns and her sister Lizzie (both working class Irish immigrants), provided detailed observations. In letters and notes, he described the systematic ruin of the country through centuries of conquest, land expropriation, forced migration, famine and economic subordination. The treatment of the Irish by English colonialism was the laboratory for pioneering colonialism in Africa, Asia and the Caribbean.Illustration: Pariplab Chakraborty.As Engels wrote, “Ireland may be regarded as England’s first colony and as one which because of its proximity is still governed exactly in the old way, and here one can already observe that the so-called liberty of English citizens is based on the oppression of the colonies.” The Great Famine (1845-1852) exemplified this: while Ireland starved, food was exported to Britain. Marx later integrated this into Capital, showing how Irish underdevelopment and exploitation fuelled English capital accumulation – clearing land for pasture, driving emigration and creating a reserve army of labour that depressed wages in England.Their views evolved significantly. Initially hopeful that English workers would lead Irish liberation, deeper study and political experience convinced them otherwise. In a key 1869 letter to Engels, Marx declared: “Deeper study has now convinced me of the opposite. The English working class will never accomplish anything before it has got rid of Ireland. The lever must be applied in Ireland.” Irish independence became a prerequisite for English working-class victory, as anti-Irish prejudice divided the proletariat and the landed aristocracy drew strength from Irish rents.They supported the Fenians, recognising the movement’s working-class, republican character. Marx actively worked within the International Workingmen’s Association (the First International) to defend Fenian prisoners and link Irish national demands with workers’ internationalism. This was not abstract sympathy but strategic politics: national oppression in the colony weakened the imperial centre, creating openings for broader revolution. Lenin later praised their Irish policy as a model for how the proletariat of oppressor nations should relate to national liberation movements.India and the 1857 revolt: National resistance to imperial brutalityMarx’s journalism for the New-York Daily Tribune provides some of the most vivid accounts. Initially, in the early 1850s, Marx saw British rule in India as destructively progressive – breaking feudal structures, if through barbaric means and laying groundwork for future development. The 1857 Revolt (the First Indian War of Independence) marked a shift. He and Engels covered it extensively, with Engels contributing military analyses.In The Indian Revolt (September 1857), Marx condemned British hypocrisy. While criticising Sepoy atrocities, he contextualised them as a mirror of English conduct: “However infamous the conduct of the Sepoys, it is only the reflex, in a concentrated form, of England’s own conduct in India.” The Sepoys left around 6,000 dead in their battle for independence. The British responded with hundreds of thousands of killings in the wake of the rebellion’s suppression. Marx detailed torture as an “organic institution” of British financial policy, village burnings, mass hangings, and floggings. The revolt was no mere mutiny but a “national revolt.”Marx highlighted British divide-and-rule tactics – “Divide et impera” – and the economic grievances – taxation, land policies, cultural insults – that united Hindus and Muslims. Engels analysed battles, noting the insurgents’ use of guerrilla tactics and the strength of popular resistance, particularly in Oudh. Far from romanticising, they critiqued rebel shortcomings while affirming the justice of resistance to foreign domination. This coverage reflected their broader internationalism. The revolt inspired them to question unilinear “progress” narratives. Colonialism’s regenerative claims were exposed as hollow in the context of plunder and resistance. Marx’s dispatches humanised the insurgents and exposed imperial ideology, countering the racist frenzy in the British press. Their work underscored that colonised peoples were active makers of their own history, not its passive victims.American slavery: A pillar of global capitalismMarx and Engels viewed chattel slavery in the United States not as a feudal relic but as integral to modern capitalism, especially cotton production feeding British industry. They followed the Civil War (1861–1865) avidly, with Marx writing articles and letters urging support for the Union once emancipation became central. In correspondence and articles, Marx pointed out that the war pitted two social systems against each other: free labour in the capitalist North versus slavery in the South, whose expansion was existential for the slaveocracy. “The present struggle between the North and the South is, therefore, nothing but a struggle between two social systems, the system of slavery and the system of free labour.” He celebrated President Abraham Lincoln’s 1863 Emancipation Proclamation and the arming of Black soldiers as transforming the conflict into a revolutionary war. Crucially, Marx linked this to European labour: “Labor in a white skin cannot emancipate itself where it is branded in a black skin.”Slavery’s overthrow cleared the ground for the US working-class movement, sparking the eight-hour day agitation, among other things. It is the historic moment that led to worldwide celebrations of May Day ever since. The revolutionary duo opposed British ruling-class sympathy for the pro-slavery Confederacy (driven by their interests in King Cotton) and mobilised within the International for solidarity with the North. They were among the first to realise that the American Civil War was centrally about one thing: war on slavery. And they welcomed it with open arms.Indeed, the concept of ‘wage slavery’ is directly connected to Marx’s correspondence with German revolutionary exiles for the 1948 revolutions who joined the Union armies in the American civil war. Engels and Marx saw slavery’s global connections – Irish famine emigrants entering Northern factories, Indian cotton alternatives, and the hypocrisy of “free trade” imperialism. Their stance combined anti-racism, anti-slavery militancy, and class analysis, rejecting any notion that economic “progress” justified human bondage.True internationalists: Solidarity across bordersWhat unified these positions was a consistent internationalism. Marx and Engels rejected chauvinism within the workers’ movement. They insisted that English workers must support Irish self-determination not out of charity, but because national oppression at home undermined their own emancipation. They applied similar logic elsewhere, seeing alliances between metropolitan proletarians and colonial resisters as essential.Their collaboration was symbiotic: Marx’s theoretical depth complemented Engels’ empirical breadth, industrial experience in Manchester, and military knowledge. Together, they produced a body of work – letters, articles, notes – that influenced later anti-colonial thinkers from Lenin to figures in the Global South. They understood capitalism as a world system, with exploitation in colonies and peripheries reinforcing it at the core.Critics sometimes portray Marx as initially Eurocentric, citing early Communist Manifesto passages on colonialism’s battering of “Chinese walls.” His and Engels’ evolution, particularly after the 1850s, shows a willingness to learn from events. They never abandoned the idea that advanced capitalist countries held key contradictions, but recognised the revolutionary potential of national liberation struggles.In an era of renewed great-power competition, and an even more aggressive American imperial offensive on a global scale by the second Trump administration, the work and example of Marx and Engels has become more relevant than ever. The iron laws of the empire meet their implacable foes in the heroic struggles against colonialism and imperialism in Cuba, Venezuela, Iran, Gaza, Ireland, Spain – indeed, the world over. And the forces against the imperial status quo are rising all over the globe, including in the very heartlands of western empire.Inderjeet Parmar is professor of international politics and associate dean of research in the School of Policy and Global Affairs at City St George’s, University of London. He is a Fellow of the Academy of Social Sciences and writes the American Imperium column for The Wire. His Twitter handle is @USEmpire. He is the author of several books, including Foundations of the American Century, and is currently writing on the history of the US foreign policy establishment, and Trump and the crisis of American Empire.