REVOLUTIONARY TERROR VERSUS REVOLUTIONARY VIOLENCE
1 When Marx used the phrase 'revolutionärer Terror' ('Neue Rheinische Zeitung', 7 November 1848) he almost certainly had the French Reign of Terror in mind. He also had not thought politics through to the depth of his later years. I suggest that while Marx never repudiated revolutionary violence, he came to see the Reign of Terror in a different and unsympathetic perspective. Revolutiomary terror he later turned against, violence he never did. 'Marx' should often read 'Marx and Engels' since their views on revolution were jointly developed. This is important in para. 7. I set violence and terror apart :
2 Marx's references to violence are fragmentary. There is no extended, detailed treatment anywhere in his work.
3 Materials are to hand, however, for revolutionary violence. In 1844-48 (roughly) Marx envisages 'total revolution, 'the shock of body against body' in the attempt to gain control of private property and the state. This means 'combat or death, bloody struggle or extinction' (Marx, 'The Poverty of Philosophy', Moscow, 1847/ 1975, 161. )
4 1848-70 : the key event here is the Paris Commune. Marx did not approve of the Commune's tactics in many respects but he wrote that : 'Collisions proceeding from the very conditions of bourgeois society must be fought out to the end, they cannot be conjured out of existence' (Marx, Collected Works, Moscow, 1977, 144, 149. 'To the end' suggests the kind of 'combat or death' scenario of the 1844-48 period.
5 1870+ : At the London Conference of the International (1871) Marx said : 'the governments are opposed to us : we must answer them with all the means that are at our disposal ... We must declare to the governments : we will proceed against you where it is possible and by force of arms when it may be necessary' (cited in D. McLellan, 'Karl Marx : His Life and Thought', London, 1973, 406.
6 The language varies but Marx seems to regard revolution as inevitable, possibly peaceful but more likely to be violent in the sense of the phrases I've quoted.
7 As said at the start 'terror' came to Marx's mind because of the experience of the last great revolution - the French Revolution with its Reign of Terror. It was the young Marx, not the mature Marx, who spoke readily of 'terror'. There is reason to believe that he came to reject 'terror' in the sense of the 'Reign of Terror' in France, 1793. Engels, whom we may take as speaking for him, says (1871 - after the Commune) : 'Thanks to the endless small terrors of the French, we can now have a better understanding of the Reign of Terror. We take it to mean the rule of the people who inspire terror. On the contrary, it is the rule of people who are themselves terror-stricken. Terror implies mostly useless cruelties perpetrated by frightened people to reassure themselves. I am convinced that we can attribute almost in its entirely the reign of Terror anno 1793 to petit-bourgeois philistines who soiled their trousers from fear, and to the dregs of the population' (see G Fabian, 'Karl Marx, Prince of Darkness', Xlibris, 2011, 524 for ref.).
8 Marx, then, endorsed revolutionary violence but saw it, so I read the quotes, as marking a time of drastic conflict in which private property and the state apparats would be taken over by the revolutionary class. He did not envisage the revolution as being followed by an extended period of terror such as occurred paradigmatically in Soviet Russia.